4 This file contains complete lists of four kinds of Exim option:
6 1. Those that can appear in the run time configuration file;
7 2. Those that can be used on the command line;
8 3. Those that can appear in the build time configuration (Local/Makefile);
9 4. Those that can appear in the build time configuration for the Exim monitor
12 This file was last updated for Exim release 4.72.
18 As Exim has developed, new options have been added at each major release. For
19 the most part, backwards compatibility has been maintained, and obsolete
20 options continue to be recognized. However, incompatible changes took place at
21 releases 3.00, and 4.00. In both cases, several groups of options were
22 amalgamated into new, extended options, and obsolete options were removed.
24 The table below contains a complete list of all Exim's current options, along
25 with their types, default values, and where they can be used. String options
26 that are expanded before use are marked with *. Host lists, domain lists, and
27 address lists are always expanded. In some cases the defaults are not fixed
28 values, or not short enough to fit in the table. These are indicated by +. Some
29 other default values are determined when the Exim binary is compiled; these are
32 For options that are specific to a particular driver, the fourth column
33 contains the driver name, for example, appendfile. Otherwise, it contains
35 . `main' for options that appear in the main section of Exim's configuration
38 . `authenticators' for generic options that apply to any authenticator;
40 . `routers' for generic options that apply to any router;
42 . `transports' for generic options that apply to any transport.
44 The fifth column contains the version of Exim in which the option was added, or
45 substantially changed. Where no number is given, the option has been in Exim
46 since the very early releases. The routers were completely reorganised for
47 release 4.00, and so no router options are shown as earlier than 4.00, though
48 in fact some of them were inherited from earlier versions.
50 -----------------------------------------------------------------------------------------
51 accept_8bitmime boolean true main 1.60 changed to true in 4.80
52 acl_not_smtp string* unset main 4.11
53 acl_not_smtp_mime string* unset main 4.51 with content scan
54 acl_smtp_auth string* unset main 4.00
55 acl_smtp_connect string* unset main 4.11
56 acl_smtp_data string* unset main 4.00
57 acl_smtp_data_prdr string* unset main 4.82 with experimental_prdr, 4.83 unless disable_prdr
58 acl_smtp_dkim string* unset main 4.70 unless disable_dkim
59 acl_smtp_etrn string* unset main 4.00
60 acl_smtp_expn string* unset main 4.00
61 acl_smtp_helo string* unset main 4.20
62 acl_smtp_mail string* unset main 4.11
63 acl_smtp_mailauth string* unset main 4.21
64 acl_smtp_mime string* unset main 4.50 with content scan
65 acl_smtp_predata string* unset main 4.43
66 acl_smtp_quit string* unset main 4.43
67 acl_smtp_rcpt string* unset main 4.00
68 acl_smtp_starttls string* unset main 4.11
69 acl_smtp_vrfy string* unset main 4.00
70 address_data string* unset routers 4.00
71 address_retry_include_sender boolean true smtp 4.64
72 address_test boolean true routers 4.14
73 admin_groups string list unset main 3.02
74 allow_domain_literals boolean false main 4.00 replacing forbid_domain_literals
75 allow_commands string list* unset pipe 1.89
76 allow_defer boolean false redirect 4.00
77 allow_fail boolean false redirect 4.00
78 allow_filter boolean false redirect 4.00
79 allow_freeze boolean false redirect 4.00
80 allow_fifo boolean false appendfile 3.13
81 allow_localhost boolean false smtp 1.73
82 allow_mx_to_ip boolean false main 3.14
83 allow_symlink boolean false appendfile
84 allow_utf8_domains boolean false main 4.14
85 arc_sign string* unset smtp 4.91 with Experimental_ARC
86 auth_advertise_hosts host list "*" main 4.00
87 authenticated_sender string* unset smtp 4.14
88 authenticated_sender_force boolean false smtp 4.61
89 authenticate_hosts host list unset smtp 3.13
90 auto_thaw time 0s main
91 av_scanner string* + main 4.50 with content scan
92 batch_id string unset appendfile 4.00
95 batch_max integer 100 appendfile
98 bcc string* unset autoreply
99 bi_command string unset main
100 body_only boolean false transports 2.05
101 bounce_message_file string unset main 4.00
102 bounce_message_text string unset main 4.00
103 bounce_return_body boolean true main 4.23
104 bounce_return_message boolean true main 4.00
105 bounce_return_size_limit int 100K main 4.23 better name for return_size_limit
106 bounce_sender_authentication string unset main 4.00
107 callout_domain_negative_expire time 3h main 4.11
108 callout_domain_positive_expire time 7d main 4.11
109 callout_negative_expire time 2h main 4.11
110 callout_positive_expire time 24h main 4.11
111 callout_random_local_part string* + main 4.11
112 cannot_route_message string* unset routers 4.11
113 caseful_local_part boolean false routers 4.00
114 cc string* unset autoreply
115 check_ancestor boolean false redirect 4.00
116 check_group boolean false appendfile
118 check_local_user boolean false routers 4.00
119 check_log_inodes integer 0 main
120 check_log_space integer 0 main
121 check_owner boolean true appendfile 3.14
123 check_rfc2047_length boolean true main 4.60
124 check_secondary_mx boolean false dnslookup 4.00
125 check_spool_inodes integer 0 main
126 check_spool_space integer 0 main
127 check_string string "From " appendfile 3.03
129 check_srv string* unset dnslookup 4.31
130 client_condition string* unset authenticators 4.68
131 client_ignore_invalid_base64 boolean false plaintext 4.61
132 client_name string* + cram_md5 3.10
133 client_secret string* unset cram_md5 3.10
134 client_send string* unset plaintext 3.10
135 client_send string* unset external (auth) 4.93
136 command string* unset lmtp 3.20
138 unset queryprogram 4.00
139 command_group string unset queryprogram 4.00
140 command_timeout time 5m smtp
141 command_user string unset queryprogram 4.00
142 commandline_checks_require_admin boolean false main 4.90
143 condition string* unset routers 4.00
144 connect_timeout time 0s smtp 1.60
145 connection_max_messages integer 500 smtp 4.00 replaces batch_max
146 create_directory boolean true appendfile
147 create_file string "anywhere" appendfile
148 current_directory string unset transports 4.00
149 unset queryprogram 4.00
150 daemon_smtp_ports string unset main 1.75 pluralised in 4.21
151 daemon_startup_retries int 9 main 4.52
152 daemon_startup_sleep time 30s main 4.52
153 dane_require_tls_ciphers string* unset smtp 4.91
154 data string unset redirect 4.00
155 data_timeout time 5m smtp
156 debug_print string* unset authenticators 4.00
158 unset transports 2.00
159 debug_store boolean false main 4.90
160 delay_after_cutoff boolean true smtp
161 delay_warning time list 24h main
162 delay_warning_condition string* + main 1.73
163 deliver_drop_privilege boolean false main 4.00
164 deliver_queue_load_max fixed-point unset main 1.70
165 delivery_date_add boolean false transports
166 delivery_date_remove boolean true main
167 dkim_canon string* unset smtp 4.70
168 dkim_domain string list* unset smtp 4.72
169 dkim_private_key string* unset smtp 4.70
170 dkim_selector string* unset smtp 4.70
171 dkim_sign_headers string* (RFC4871) smtp 4.70
172 dkim_strict string* unset smtp 4.70
173 dkim_timestamps integer* unset smtp 4.92
174 dkim_verify_hashes string sha256:sha512:sha1 main 4.93
175 dkim_verify_keytypes string ed25519:rsa main 4.93
176 dkim_verify_minimal boolean false main 4.93
177 dkim_verify_signers string* $dkim_signers main 4.70
178 directory string* unset appendfile
179 directory_file string* + appendfile
180 directory_mode octal-integer 0700 appendfile
181 directory_transport string* unset redirect 4.00
182 disable_ipv6 boolean false main 4.61
183 disable_logging boolean false routers 4.11
184 false transports 4.11
185 dmarc_forensic_sender string unset main 4.82 if experimental_dmarc
186 dmarc_history_file string unset main 4.82 if experimental_dmarc
187 dmarc_tld_file string unset main 4.82 if experimental_dmarc
188 dns_again_means_nonexist domain list unset main 1.89
189 dns_check_names_pattern string + main 2.11
190 dns_cname_loops integer 0 main 4.92 Set to 9 for older behaviour
191 dns_csa_search_limit integer 5 main 4.60
192 dns_csa_use_reverse boolean true main 4.60
193 dns_dnssec_ok integer -1 main 4.82
194 dns_dane_ok integer -1 main 4.83
195 dns_ipv4_lookup boolean false main 3.20
196 dns_qualify_single boolean true smtp
197 dns_retrans time 0s main 1.60
198 dns_retry integer 0 main 1.60
199 dns_search_parents boolean false smtp
200 dns_use_edns0 integer -1 main 4.76
201 domains domain list unset routers 4.00
202 driver string unset authenticators
205 drop_cr boolean false main 4.00 became a no-op in 4.21
206 dscp string unset smtp 4.82
207 dsn_from string* + main 4.67
208 envelope_to_add boolean false transports
209 envelope_to_remove boolean true main
210 environment string* unset pipe 2.95
211 errors_copy string list* unset main
212 errors_reply_to string unset main
213 errors_to string* unset routers 4.00
214 escape_string string ">From " appendfile 3.03
216 exim_group string ++ main
217 exim_path string ++ main
218 exim_user string ++ main
219 exim_version string ++ main 4.93
220 expn boolean true routers
221 extra_local_interfaces string unset main 4.21
222 extract_addresses_remove_arguments boolean true main 1.92
223 fail_verify boolean false routers
224 fail_verify_recipient boolean false routers 4.00
225 fail_verify_sender boolean false routers 4.00
226 fallback_hosts string list unset routers 4.00
228 file string* unset appendfile
231 file_expand boolean false autoreply
232 file_format string unset appendfile 3.03
233 file_must_exist boolean false appendfile
234 file_optional boolean false autoreply
235 file_transport string* unset redirect 4.00
236 filter_prepend_home boolean true redirect 4.63
237 final_timeout time 10m smtp
238 finduser_retries integer 0 main
239 forbid_blackhole boolean false redirect 4.00
240 forbid_exim_filter boolean false redirect 4.44
241 forbid_fail boolean false redirect 4.00
242 forbid_file boolean false redirect 4.00
243 forbid_filter_existstest boolean false redirect 4.00
244 forbid_filter_logwrite boolean false redirect 4.00
245 forbid_filter_lookup boolean false redirect 4.00
246 forbid_filter_perl boolean false redirect 4.00
247 forbid_filter_readfile boolean false redirect 4.00
248 forbid_filter_readsocket boolean false redirect 4.11
249 forbid_filter_reply boolean false redirect 4.00
250 forbid_filter_run boolean false redirect 4.00
251 forbid_include boolean false redirect 4.00
252 forbid_pipe boolean false redirect 4.00
253 forbid_sieve_filter boolean false redirect 4.44
254 forbid_smtp_code boolean false redirect 4.63
255 force_command boolean false pipe 4.82
256 freeze_exec_fail boolean false pipe 1.89
257 freeze_signal boolean false pipe 4.75
258 freeze_tell boolean false main 4.00 replaces freeze_tell_mailmaster
259 from string* unset autoreply
260 gecos_name string* unset main
261 gecos_pattern string unset main
262 gethostbyname boolean false smtp
263 gnutls_allow_auto_pkcs11 boolean false main 4.82
264 gnutls_compat_mode boolean unset main 4.70
265 gnutls_require_kx string* unset main 4.67 deprecated, warns
266 string* unset smtp 4.67 deprecated, warns
267 gnutls_require_mac string* unset main 4.67 deprecated, warns
268 string* unset smtp 4.67 deprecated, warns
269 gnutls_require_protocols string* unset main 4.67 deprecated, warns
270 string* unset smtp 4.67 deprecated, warns
271 group string + routers 4.00
272 unset transports 4.00 replaces local option in some transports
273 header_line_maxsize integer 0 (unset) main 4.14
274 header_maxsize integer 1M main 4.14
275 headers string* unset autoreply
276 headers_add string* unset routers 4.00
278 headers_charset string ++ main 4.21
279 headers_only boolean false transports 2.05
280 headers_remove string* unset routers 4.00
282 headers_rewrite string unset transports 3.20
283 helo_accept_junk_hosts host list unset main 3.00
284 helo_allow_chars string "" main 4.02
285 helo_lookup_domains domain list unset main 4.00
286 helo_data string* "$primary_hostname" smtp 3.21
287 helo_try_verify_hosts host list unset main 4.00
288 helo_verify_hosts host list unset main 1.73
289 hide_child_in_errmsg false redirect 4.00
290 hold_domains domain list unset main 1.70
291 home_directory string* unset transports 4.00 replaces individual options
292 host_all_ignored string "defer" manualroute 4.67
293 host_find_failed string "freeze" manualroute 4.00
294 host_lookup host list unset main 3.00
295 host_lookup_order string list "bydns:byaddr" main 4.30
296 host_reject_connection host list unset main 4.00
297 hosts string unset iplookup 4.00
298 string list* unset smtp
299 hosts_avoid_esmtp host list unset smtp 4.21
300 hosts_avoid_pipelining host list unset smtp 4.67
301 hosts_avoid_tls host list unset smtp 3.20
302 hosts_connection_nolog host list unset main 4.43
303 hosts_max_try integer 5 smtp 3.20
304 hosts_max_try_hardlimit integer 50 smtp 4.50
305 hosts_nopass_tls host list unset smtp 4.00
306 hosts_noproxy_tls host list "*" smtp 4.90
307 hosts_override boolean false smtp 2.11
308 hosts_pipe_connect host_list unset smtp 4.93 if experimental_pipe_connect
309 hosts_randomize boolean false manualroute 4.00
311 hosts_require_auth host list unset smtp 4.00
312 hosts_require_dane host list unset smtp 4.91 (4.85 experimental)
313 hosts_require_ocsp host list unset smtp 4.82 if experimental_ocsp
314 hosts_require_tls host list unset smtp 3.20
315 hosts_treat_as_local domain list unset main 1.95
316 hosts_try_auth host list unset smtp 4.00
317 hosts_try_dane host list unset smtp 4.91 (4.85 experimental)
318 hosts_try_fastopen host list unset smtp 4.88
319 hosts_try_prdr host list unset smtp 4.82 if experimental_prdr
320 ibase_servers string unset main 4.23
321 ignore_bounce_errors_after time 0s main 4.00
322 ignore_eacces boolean false redirect 4.00
323 ignore_enotdir boolean false redirect 4.00
324 ignore_fromline_hosts host list unset main
325 ignore_fromline_local boolean false main 2.05
326 ignore_status boolean false pipe
327 ignore_target_hosts host list unset routers 4.00
328 include_directory string unset redirect 4.00
329 initgroups false routers 4.00
330 interface string list unset smtp 1.70
331 keep_malformed time 4d main
332 keepalive boolean true smtp 2.05
333 ldap_default_servers string list unset main 3.02
334 ldap_version int 2 or 3 main 4.14
335 local_from_check boolean true main 3.14
336 local_from_prefix string unset main 3.14
337 local_from_suffix string unset main 3.14
338 local_interfaces string list unset main 1.60
339 local_part_prefix string unset routers 4.00 replaces prefix
340 local_part_prefix_optional boolean unset routers 4.00 replaces prefix_optional
341 local_part_suffix string unset routers 4.00 replaces suffix
342 local_part_suffix_optional boolean unset routers 4.00 replaces suffix_optional
343 local_parts string list* unset routers 4.00
344 local_scan_timeout time 5m main 4.03
345 local_sender_retain boolean false main 4.00
346 localhost_number string unset main
347 lock_fcntl_timeout time 0s appendfile 3.14
348 lock_flock_timeout time 0s appendfile 4.11
349 lock_interval time 3s appendfile
350 lock_retries integer 10 appendfile
351 lockfile_mode octal-integer 0600 appendfile
352 lockfile_timeout time 30m appendfile
353 log string* unset autoreply
354 log_as_local boolean + routers 4.00
355 log_file_path string list ++ main
356 log_defer_output boolean false pipe 1.89
357 log_fail_output boolean false pipe 1.60
358 log_output boolean false pipe 1.60
359 log_selector string unset main 4.00
360 log_timezone boolean false main 4.11
361 lookup_open_max integer 25 main 2.05
362 mailbox_filecount string* unset appendfile 4.43
363 mailbox_size string* unset appendfile 4.43
364 maildir_format boolean false appendfile 1.70
365 maildir_retries integer 10 appendfile 1.70
366 maildir_tag string* unset appendfile 1.92
367 maildir_use_size_file boolean* false appendfile 4.30 expanded in 4.77
368 maildirfolder_create_regex string unset appendfile 4.62
369 mailstore_format boolean false appendfile 2.00
370 mailstore_prefix string* unset appendfile 2.00
371 mailstore_suffix string* unset appendfile 2.00
372 match_directory string* unset localuser
373 max_output integer 20K pipe
374 max_rcpt integer 100 smtp 1.60
375 max_user_name_length integer 0 main
376 mbx_format boolean false appendfile 2.10
377 message_body_newlines boolean false main 4.68
378 message_body_visible integer 500 main
379 message_id_header_domain string* unset main 4.11
380 message_id_header_text string* unset main
381 message_logs boolean true main 4.10
382 message_prefix string* + appendfile 4.00 replaces prefix
383 string* unset pipe 4.00 replaces prefix
384 message_size_limit integer 50M main
386 message_suffix string* + appendfile 4.00 replaces suffix
387 string* unset pipe 4.00 replaces suffix
388 mode octal-integer 0600 appendfile
390 mode_fail_narrower boolean true appendfile 1.70
391 modemask octal-integer 022 redirect 4.00
392 more boolean true routers 4.00
393 move_frozen_messages boolean false main 3.09
394 multi_domain boolean true smtp
395 mx_domains domain list unset dnslookup 4.00
396 mx_fail_domains domain list unset dnslookup 4.43
397 mysql_servers string list unset main 3.03
398 never_users string list unset main
399 notify_comsat boolean false appendfile
400 once string* unset autoreply
401 once_file_size integer 0 autoreply 3.20
402 once_repeat time 0s autoreply 2.95
403 one_time boolean false redirect 4.00
404 openssl_options string +no_sslv2 main 4.73 default changed in 4.80
405 optional boolean false iplookup 4.00
406 oracle_servers string unset main 4.00
407 owners string list unset redirect 4.00
408 owngroups string list unset redirect 4.00
409 pass_on_timeout boolean false routers 4.00
410 pass_router string unset routers 4.00
411 path string "/usr/bin" pipe
412 percent_hack_domains domain list unset main
413 perl_at_start boolean false main 2.10
414 perl_startup string unset main 2.10
415 permit_coredump boolean false pipe 4.73
416 pgsql_servers string list unset main 3.14
417 pid_file_path string ++ main
418 pipe_as_creator boolean false pipe
419 pipe_transport string* unset redirect 4.00
420 pipelining_advertise_hosts host list "*" main 4.14
421 pipelining__connect_advertise_hosts host list "*" main 4.92 if experimental_pipe_connect
422 port integer 0 iplookup 4.00
424 preserve_message_logs boolean false main
425 prdr_enable boolean false main 4.82 if experimental_prdr
426 primary_hostname string + main
427 print_topbitchars boolean false main 1.89
428 process_log_path string unset main 4.21
429 prod_requires_admin boolean true main 1.70
430 protocol string "udp" iplookup 4.00
431 string "smtp" smtp 3.20
432 public_name string unset authenticators 3.10
433 qualify_domain string + main
434 string* unset redirect 4.31
435 qualify_preserve_domain boolean false redirect 4.00
436 qualify_recipient string + main
437 qualify_single boolean true dnslookup 4.00
438 query string* + iplookup 4.00
439 queue_domains domain list unset main 4.00
440 queue_list_requires_admin boolean true main 1.95
441 queue_only boolean false main
442 queue_only_file string unset main 2.05
443 queue_only_load fixed-point unset main
444 queue_only_load_latch boolean true main 4.68
445 queue_only_override boolean true main 4.21
446 queue_run_in_order boolean false main 1.70
447 queue_run_max integer 5 main
448 queue_smtp_domains domain list unset main
449 quota string* unset appendfile 1.60
450 quota_directory string* unset appendfile 4.11
451 quota_filecount integer 0 appendfile 2.05
452 quota_is_inclusive boolean true appendfile 3.20
453 quota_size_regex string unset appendfile 3.14
454 quota_warn_message string* + appendfile 2.10
455 quota_warn_threshold string* 0 appendfile 2.10
456 rcpt_include_affixes boolean false transports 4.21
457 receive_timeout time 0s main 4.00 replacing accept_timeout
458 received_header_text string* + main
459 received_headers_max integer 30 main
460 recipient_unqualified_hosts host list unset main 4.00 replacing receiver_unqualified_hosts
461 recipients_max integer 0 main 1.60
462 recipients_max_reject boolean false main 1.70
463 redirect_router string unset routers 4.00
464 remote_max_parallel integer 1 main
465 remote_sort_domains domain list unset main 4.00 replacing remote_sort
466 repeat_use boolean true redirect 4.00
467 reply_to string* unset autoreply 2.05
468 reply_transport string* unset redirect 4.00
469 require_files string list* unset routers 4.00
470 reroute string* unset iplookup 4.00
471 response_pattern string unset iplookup 4.00
472 restrict_to_path boolean false pipe
473 retry_data_expire time 7d main 3.03
474 retry_include_ip_address boolean true smtp 1.92
475 retry_interval_max time 24h main
476 retry_use_local_part boolean + routers 4.00
477 + transports 4.00 replacing individual options
478 return_fail_output boolean false pipe 1.60
479 return_message boolean false autoreply
480 return_output boolean false pipe
481 return_path string* unset transports 2.05
482 return_path_add boolean false transports
483 return_path_remove boolean true main
484 return_size_limit integer 100K main renamed bounce_return_size_limit in 4.23
485 rewrite boolean true redirect 4.00
486 rewrite_headers boolean true dnslookup 4.00
487 rfc1413_hosts host list * main
488 rfc1413_query_timeout time 5s main
489 router_home_directory string* unset routers 4.11
490 route_data string* unset manualroute 4.00
491 route_list string list unset manualroute 4.00
492 same_domain_copy_routing boolean false dnslookup 4.00
493 search_parents boolean false dnslookup 4.00
494 self string "freeze" routers 4.00
495 sender_unqualified_hosts host list unset main
496 senders address list unset routers 4.00
497 serialize_hosts host list unset smtp 1.60
498 server_advertise_condition string* unset authenticators 4.14
499 server_channelbinding bool false gsasl 4.80
500 server_condition string* unset authenticators 3.10 (plaintext) 4.64 (others)
501 server_hostname string* "$primary_hostname" cyrus_sasl,gsasl,heimdal_gssapi (cyrus-only) 4.80 (others)
502 server_keytab string* unset heimdal_gssapi 4.80
503 server_mail_auth_condition string* unset authenticators 3.22
504 server_mech string public_name cyrus_sasl,gsasl 4.43 (cyrus-only) 4.80 (others)
505 server_password string unset gsasl 4.80
506 server_param1 string* unset tls (auth) 4.86
507 server_param2 string* unset tls (auth) 4.86
508 server_param3 string* unset tls (auth) 4.86
509 server_param2 string* unset tls (auth) 4.86 (tls-only) 4.93 (external)
510 server_param3 string* unset tls (auth) 4.86 (tls-only) 4.93 (external)
511 server_prompts string* unset plaintext 3.10
512 server_realm string unset cyrus_sasl,gsasl 4.43 (cyrus-only) 4.80 (others)
513 server_scram_iter string* unset gsasl 4.80
514 server_scram_salt string* unset gsasl 4.80
515 server_secret string* unset cram_md5 3.10
516 server_service string "smtp" cyrus_sasl,gsasl,heimdal_gssapi (cyrus-only) 4.80 (others)
517 server_set_id string* unset authenticators 3.10
518 set string* unset routers 4.93
519 shadow_condition string* unset transports
520 shadow_transport string unset transports
521 size_addition integer 1024 smtp 1.91
522 skip_syntax_errors boolean false redirect 4.00
523 smtp_accept_keepalive boolean true main
524 smtp_accept_max integer 20 main
525 smtp_accept_max_nonmail integer 10 main 4.11
526 smtp_accept_max_nonmail_hosts host list * main 4.14
527 smtp_accept_max_per_connection integer 1000 main 4.00
528 smtp_accept_max_per_host integer 0 main 2.05
529 smtp_accept_queue integer 0 main
530 smtp_accept_queue_per_connection integer 10 main 2.03
531 smtp_accept_reserve integer 0 main
532 smtp_active_hostname string* unset main 4.33
533 smtp_banner string* + main
534 smtp_check_spool_space boolean true main 2.10
535 smtp_connect_backlog integer 5 main
536 smtp_enforce_sync boolean true main 4.00
537 smtp_etrn_command string* unset main 1.92
538 smtp_etrn_serialize boolean true main 1.89
539 smtp_load_reserve fixed-point unset main
540 smtp_max_synprot_errors integer 3 main 4.30
541 smtp_max_unknown_commands integer 3 main 4.14
542 smtp_ratelimit_hosts host list unset main 4.00
543 smtp_ratelimit_mail string unset main 4.00
544 smtp_ratelimit_rcpt string unset main 4.00
545 smtp_receive_timeout time 5m main
546 smtp_reserve_hosts host list unset main
547 smtp_return_error_details boolean false main 4.11
548 socket string* unset lmtp 4.11
549 spamd_address string* + main 4.50 with content scan
550 split_spool_directory boolean false main 1.70
551 spool_directory string ++ main
552 spool_wireformat boolean false main 4.90
553 sqlite_lock_timeout time 5s main 4.53
554 strict_acl_vars boolean false main 4.64
555 srv_fail_domains domain list unset dnslookup 4.43
556 strip_excess_angle_brackets boolean false main
557 strip_trailing_dot boolean false main
558 subject string* unset autoreply
559 syntax_errors_text string* unset redirect 4.00
560 syntax_errors_to string unset redirect 4.00
561 syslog_duplication boolean true main 4.21
562 syslog_facility string unset main 4.20
563 syslog_processname string "exim" main 4.20
564 syslog_timestamp boolean true main 4.00
565 system_filter string unset main 4.00 replacing message_filter
566 system_filter_directory_transport string unset main 4.00 replacing message_filter
567 system_filter_file_transport string unset main 4.00 replacing message_filter
568 system_filter_group string unset main 4.00 replacing message_filter
569 system_filter_pipe_transport string unset main 4.00 replacing message_filter
570 system_filter_reply_transport string unset main 4.00 replacing message_filter
571 system_filter_user string unset main 4.00 replacing message_filter
572 tcp_nodelay boolean true main 4.23
574 tcp_wrappers_daemon_name string* ++ main 4.73
575 temp_errors string list + pipe 1.95
576 text string* unset autoreply
577 timeout time 5m lmtp 3.20
581 timeout_defer boolean false pipe 4.51
582 timeout_frozen_after time 0s main 3.20
583 timezone string + main 3.15
584 tls_advertise_hosts host list * main 3.20
585 tls_advertise_requiretls host list * main 4.92 if experimental_requiretls
586 tls_certificate string* unset main 3.20
588 tls_dh_max_bits integer 2236 main 4.80
589 tls_dh_min_bits integer 1024 smtp 4.82
590 tls_dhparam string* unset main 3.20
591 tls_ocsp_file string* unset main 4.80 if experimental_ocsp
592 tls_on_connect_ports string unset main 4.43
593 tls_privatekey string* unset main 3.20
595 tls_remember_emstp boolean false main 4.21
596 tls_require_ciphers string* unset smtp 4.00 replaces tls_verify_ciphers
597 string* unset main 4.33
598 tls_sni string* unset main 4.80
599 tls_tempfail_tryclear boolean true smtp 4.05
600 tls_try_verify_hosts host list unset main 4.00
601 tls_verify_certificates string* unset main 3.20
603 tls_verify_hosts host list unset main 3.20
604 to string* unset autoreply
605 translate_ip_address string unset routers 4.00
606 transport string* unset routers 4.00
607 transport_current_directory string unset routers 4.00
608 transport_home_directory string unset routers 4.00
609 transport_filter string unset transports
610 transport_filter_timeout time 5m transports 4.30
611 trusted_groups string list unset main
612 trusted_users string list unset main
613 umask octal-integer 022 pipe
614 unknown_login string unset main
615 unknown_username string unset main
616 unseen boolean false routers 4.00
617 untrusted_set_sender boolean false main 3.20
618 use_bsmtp boolean false appendfile 4.00
620 use_crlf boolean false appendfile 1.89
622 use_fcntl_lock boolean + appendfile 1.70
623 use_flock_lock boolean + appendfile 4.11
624 use_lockfile boolean + appendfile
625 use_mbx_lock boolean + appendfile 2.10
626 use_shell boolean false pipe 1.70
627 user string + routers 4.00
628 unset transports 4.00 replaces individual options
629 utf8_downconvert integer unset smtp 4.92 if SUPPORT_I18N
630 uucp_from_pattern string + main 1.75
631 uucp_from_sender string* "$1" main 1.75
632 verify boolean true routers 4.00
633 verify_only boolean false routers 4.00
634 verify_recipient boolean true routers 4.00
635 verify_sender boolean true routers 4.00
636 warn_message_file string unset main 4.00
637 widen_domains string list unset dnslookup 4.00
638 write_rejectlog boolean true main 4.31
642 2. COMMAND LINE OPTIONS
643 -----------------------
645 The table below contains a complete list of all Exim's command line options.
646 Those marked with # are available only to trusted users, those marked with +
647 are available only to admin users, and those marked with * exist only to
648 provide compatibility with Sendmail.
651 --help Give a little help (not a lot)
652 --version Give version information (alias for -bV)
655 -bdf + Start daemon and run it in the foreground
656 -be Test string expansion
657 -bem Test string expansion, read test message first
658 -bF Test system filter file
659 -bf Test user filter file
660 -bfd Set domain for filter testing
661 -bfl Set local part for filter testing
662 -bfp Set local part prefix for filter testing
663 -bfs Set local part suffix for filter testing
664 -bh Test incoming SMTP call, omitting callouts
665 -bhc Test incoming SMTP call, with callouts
666 -bi * Run <command>bi_command</command>
667 -bI:help Show list of accepted -bI:<tag> options
668 -bm Accept message on standard input
669 -bmalware + Invoke configured malware scanning against supplied filename
670 -bnq Don't qualify addresses in locally submitted messages
671 -bP Show configuration option settings
673 -bpa + ... with generated addresses as well
674 -bpc + ... but just show a count of messages
675 -bpr + ... do not sort
676 -bpra + ... with generated addresses, unsorted
677 -bpru + ... only undelivered addresses, unsorted
678 -bpu + ... only undelivered addresses
679 -brt Test retry rules
680 -brw Test rewriting rules
681 -bS Read batch SMTP on standard input
682 -bs Run SMTP on standard input and output
683 -bt Test address directing and routing
684 -bV Verify version number
685 -bv Test recipient address verification
686 -bvs Test sender address verification
687 -bw + Inetd wait mode
688 -C + Use alternate configuration file
689 -D + Define macro for configuration file
690 -d + Turn on debugging output
691 -dd + Ditto, but if a daemon, not for subprocesses
692 -dropcr Remove CR character in input: became a no-op in 4.21
694 -ex * Synonym for -oex (for several different x)
695 -F Set calling user name
696 -f # Set calling user address
699 -i Dot does not terminate message
700 -M + Force deliver specific message
701 -Mar + Add recipient to message
702 -MC Internal use only
703 -MCA Internal use only
704 -MCP Internal use only
705 -MCQ Internal use only
706 -MCS Internal use only
707 -MCT Internal use only
708 -Mc + Deliver specific message
709 -Mes + Edit message sender
710 -Mf + Freeze message(s)
711 -Mg + Give up (bounce) message(s)
712 -Mmad + Mark all recipients delivered
713 -Mmd + Mark one recipient delivered
714 -Mrm + Remove message(s) (no bounce)
715 -Mset + Load message's variables when testing with -be
716 -Mt + Thaw message(s)
717 -Mvb + View message body
718 -Mvc + View entire message in RFC 2822 format
719 -Mvh + View message header
720 -Mvl + View message log
722 -N + Deliver without transporting
725 -oA * Supply argument for <option>-bi</option>
726 -oB Set max messages down one connection
727 -odb Background delivery
728 -odf Foreground delivery
729 -odi Foreground delivery
730 -odq Queue message; do not deliver
731 -odqs ... do not do SMTP deliveries
732 -oee Error sent by mail; zero return code
733 -oem Error sent by mail; non-zero return code
734 -oep Error written to standard error stream
735 -oeq * Error written to standard error stream
736 -oew * Error sent by mail; non-zero return code
737 -oi Dot does not terminate message
738 -oitrue * Dot does not terminate message
739 -oMa # Supply host address
740 -oMaa # Supply authenticator name
741 -oMai # Supply authenticated id
742 -oMas # Supply authenticated sender
743 -oMi # Supply interface address
744 -oMm # Supply message reference
745 -oMr # Supply protocol name
746 -oMs # Supply host name
747 -oMt # Supply ident string
750 -oP * Specify path for daemon's pid file
751 -or Timeout non-SMTP messages
752 -os Timeout for SMTP messages
753 -ov * Verbose; same as -v
754 -oX Alternative port for daemon
755 -pd Delay Perl interpreter start
756 -ps Do not delay Perl interpreter start
757 -p<r>:<s> * Same as -oMr <r> -oMs <s>
759 -qf + ... force delivery ) Other combinations are
760 -qff + ... and include frozen messages ) possible. The syntax is
761 -qi + ... initial deliveries only )
762 -ql + ... local deliveries only ) -q[q][f][f][i|l][time]
763 -qq + Two-stage queue run )
766 -R Select by recipient in queue run
768 -Rff ... and frozen messages
769 -Rr ... using regular expression
770 -Rrf ... with forcing
771 -Rrff ... and frozen messages
773 -S Select by sender in queue run
775 -Sff ... and frozen messages
776 -Sr ... using regular expression
777 -Srf ... with forcing
778 -Srff ... and frozen messages
779 -Tqt * Used by Exim test suite; not recognized in normal use
780 -t Take recipients from header lines
782 -tls-on-connect Do TLS on startup (for legacy clients)
784 -v Verbose - shows SMTP dialogue and other delivery info
785 -x Ignored (AIX compatibility)
788 3. BUILD TIME OPTIONS FOR EXIM
789 ------------------------------
791 The table below contains a "mostly" complete list of options that can be
792 set in Local/Makefile when building Exim. The only items not included are
793 those whose names can be trivially derived from rules stated below.
795 More information about individual options can be found in src/EDITME and
798 The second column below gives the type of option:
800 . `system' means the option is concerned with the operating system;
802 . `driver' means the option selects a driver to be included in the binary;
804 . `lookup' means the option selects a lookuptype to be included in the binary;
806 . `mandatory' means the option is required to be supplied;
808 . `recommended' means the option is recommended to be supplied;
810 . `optional' means what it says;
812 Those marked with * are specialized and are unlikely to be required in most
813 installations. Those that are marked with ** are commonly set in OS-specific
814 Makefiles. If you use any of these in your Local/Makefile, you may need to
815 reproduce some of the OS-specific settings. For example, in the Makefile for
816 Solaris (which is actually called OS/Makefile-SunOS5), there is
818 LIBS=-lsocket -lnsl -lkstat
820 If you use LIBS to add extra libraries, you must also include the OS ones in
821 your setting. It is better, in this particular case, to use EXTRALIBS, which is
822 empty by default, and is provided for just this reason. Of course, if you do
823 actually want to modify a setting from the OS-specific file, there is nothing
824 to stop you overriding it in your Local/Makefile.
826 When building Exim with dynamically loaded lookup support, for "LOOKUP_FOO",
827 you can define "LOOKUP_FOO_INCLUDE" and "LOOKUP_FOO_LIBS", for includes and
828 libraries specific only to that module. These rules are only used where the
829 relevant lookup is a module. These options are not explicitly listed below.
831 Variables with names endined `_PC' are used for pkg-config integration; setting
832 the value to the name of a pkg-config package will cause Exim's build system to
833 query the --cflags and --libs for the given name, when building anything
834 dependent upon the component associated with the `_PC' variable. For lookups,
835 if the lookup is dynamically loaded, then this *replaces* the use of the
836 corresponding _INCLUDE and _LIBS options, which will be ignored. If the lookup
837 is statically loaded into Exim, the results will be inserted into the
838 "LOOKUP_INCLUDE" and "LOOKUP_LIBS" options. For authenticator, the results
839 will be inserted into the "CFLAGS" and "AUTH_LIBS" options. These options are
840 only listed below for the TLS implementation cases.
843 Option Type Description
844 ------------------------------------------------------------------------------
846 ALT_CONFIG_PREFIX optional restricts location of -C files
847 APPENDFILE_MODE optional*
848 APPENDFILE_DIRECTORY_MODE optional*
849 APPENDFILE_LOCKFILE_MODE optional*
850 AR system command to build a library
851 AUTH_CRAM_MD5 driver include cram_md5 authenticator
852 AUTH_CYRUS_SASL driver include Cyrus SASL authenticator
853 AUTH_GSASL driver include GNU SASL authenticator
854 AUTH_HEIMDAL_GSSAPI driver include Heimdal GSSAPI authenticator
855 AUTH_LIBS system library linkage for authenticators
856 AUTH_PLAINTEXT driver include plaintext authenticator
857 AUTH_SPA driver include SPA (NTLM) authenticator
858 AUTH_VARS=3 optional* number of $auth variables
859 BASENAME_COMMAND system** path to basename
860 BASE_62=62 optional* not normally changed for Unix
861 BIN_DIRECTORY mandatory Exim binary directory
862 CC system** C compiler
863 CFLAGS system** flags for C compiler
864 CFLAGS_DYNAMIC system** extra flags needed for .so modules
865 CHGRP_COMMAND system** path to chgrp
866 CHOWN_COMMAND system** path to chown
867 COMPRESS_COMMAND system path to a compress command
868 COMPRESS_SUFFIX system suffix added to compressed files
869 CONFIGURE_FILE mandatory Exim runtime configuration file
870 CONFIGURE_FILE_USE_EUID optional*
871 CONFIGURE_FILE_USE_NODE optional*
872 CONFIGURE_GROUP optional* alternate group for configuration file
873 CONFIGURE_OWNER optional* alternate owner for configuration file
874 CYRUS_PWCHECK_SOCKET optional socket for pwcheck daemon
875 DBMLIB optional** location of DBM library
876 DB_DIRECTORY_MODE optional* mode for hints directory
877 DB_LOCKFILE_MODE optional* mode for hints lock files
878 DB_LOCK_TIMEOUT optional* timeout for hints lock files
879 DB_MODE optional* mode for hints files
880 DEFAULT_CRYPT optional default crypt() function
881 DELIVER_IN_BUFFER_SIZE optional*
882 DELIVER_OUT_BUFFER_SIZE optional*
883 DISABLE_DKIM optional disables DKIM support
884 DISABLE_DNSSEC optional disables attempts to use DNSSEC
885 DISABLE_D_OPTION optional disables -D option
886 ERRNO_QUOTA optional* error code for system quota failures
887 EXICYCLOG_MAX optional number of old log files to keep
888 EXIMDB_DIRECTORY_MODE optional* for hints database directory
889 EXIMDB_LOCKFILE_MODE optional* for hints lock files
890 EXIMDB_MODE optional* mode for hints files
891 EXIMON_TEXTPOP system**
893 EXIM_GROUP mandatory group to use for Exim
894 EXIM_MONITOR optional set to eximon.bin to compile
896 EXIM_USER mandatory user to use for Exim
897 EXIWHAT_EGREP_ARG system** to find Exim processes from ps
898 EXIWHAT_KILL_SIGNAL system** -SIGUSR1 or numerical equivalent
899 EXIWHAT_MULTIKILL_CMD system**
900 EXIWHAT_MULTIKILL_ARG system**
901 EXIWHAT_PS_ARG system** to list all processes
902 EXIWHAT_PS_CMD system** path to ps command
903 EXPAND_LISTMATCH_RHS optional* restore pre-4.77 match_*{}{} behaviour
904 EXTRALIBS system additional libraries
905 EXTRALIBS_EXIM system additional libraries for Exim only
906 EXTRALIBS_EXIMON system additional libraries for the monitor
907 FIXED_NEVER_USERS optional can't override at runtime
908 HAVE_ICONV system the iconv() function is available
909 HAVE_IPV6 system include IPv6 support
910 HEADERS_CHARSET optional charset for decoded header lines
911 HEADER_ADD_BUFFER_SIZE optional* buffer for header_add()
912 HEADER_MAXSIZE optional* max memory for message header
913 HOSTNAME_COMMAND system** path to hostname command
914 INCLUDE system path to include files
915 INFO_DIRECTORY optional directory for Info documentation
916 INPUT_DIRECTORY_MODE optional mode for input directory
917 IPV6_INCLUDE system additional includes for IPv6
918 IPV6_LIBS system additional libraries for IPv6
919 LDAP_LIB_TYPE optional type of LDAP library
920 LFLAGS system** link editor flags
921 LIBIDENTCFLAGS system C flags when compiling libident
922 LIBIDENTNAME system name for libident library
923 LIBRESOLV system** library for DNS resolver
924 LIBS system** additional libraries
925 LIBS_EXIM system** additional libraries for Exim ony
926 LIBS_EXIMON system** additional libraries for monitor
927 LOCAL_SCAN_SOURCE optional location of local_scan() source
928 LOG_DIRECTORY_MODE optional mode for log directory
929 LOG_FILE_PATH optional path to log files
930 LOG_MODE optional mode for log files
931 LOOKUP_CDB lookup include cdb lookup
932 LOOKUP_DBM lookup include dbm lookup
933 LOOKUP_DNSDB lookup include dnsdb lookup
934 LOOKUP_DSEARCH lookup include dsearch lookup
935 LOOKUP_INCLUDE lookup include files for lookups
936 LOOKUP_LDAP lookup include ldap lookup
937 LOOKUP_LIBS lookup include libraries for lookups
938 LOOKUP_LSEARCH lookup include all lsearch lookups
939 LOOKUP_MODULE_DIR optional* where dynamic lookup modules live
940 LOOKUP_MYSQL lookup include mysql lookup
941 LOOKUP_NIS lookup include nis lookup
942 LOOKUP_NISPLUS lookup include nisplus lookup
943 LOOKUP_ORACLE lookup include oracle lookup
944 LOOKUP_PGSQL lookup include pgsql lookup
945 LOOKUP_TESTDB lookup*
946 LOOKUP_WHOSON lookup include whoson lookup
947 LOOKUP_*_INCLUDE optional* include files for dynamic module
948 LOOKUP_*_LIBS optional* libraries for dynamic module
949 MAKE_SHELL optional* shell to use for make
950 MAX_FILTER_SIZE optional* max file size for filter files
951 MAX_INCLUDE_SIZE optional* max file size for :include: files
952 MAX_LOCALHOST_NUMBER=256 optional* for when localhost_number is set
953 MAX_NAMED_LIST optional* max named lists of a given type
954 MAX_INTERFACES system maximum network interfaces
955 MSGLOG_DIRECTORY_MODE optional* mode for message log directory
956 MV_COMMAND system path to mv command
957 NO_SYMLINK optional install doesn't make 'exim" symlink
958 PCRE_CONFIG system* use pcre-config for PCRE support
959 PCRE_LIBS system* library for using PCRE
960 PERL_CC system* compiler for Perl interface code
961 PERL_CCOPTS system* flags for same
962 PERL_COMMAND system path to Perl
963 PERL_LIBS system* library for compiling Perl interface
964 PID_FILE_PATH optional path to daemon's pid file
965 RADIUS_CONFIG_FILE optional path to Radius config file
966 RADIUS_LIB_TYPE optional type of RADIUS library
967 RANLIB system** path to ranlib command
968 RM_COMMAND system path to rm command
969 ROUTER_ACCEPT driver include accept router
970 ROUTER_DNSLOOKUP driver include dnslookup router
971 ROUTER_MANUALROUTE driver include manualroute router
972 ROUTER_IPLITERAL driver include ipliteral router
973 ROUTER_IPLOOKUP driver include iplookup router
974 ROUTER_REDIRECT driver include redirect router
975 ROUTER_QUERYPROGRAM driver include queryprogram router
976 SPOOL_DIRECTORY recommended path to spool directory
977 SPOOL_DIRECTORY_MODE optional mode of spool directory
978 SPOOL_MODE optional mode of spool files
979 STRING_SPRINTF_BUFFER_SIZE optional* buffer for string_sprintf()
980 STRIP_COMMAND optional* can be used to strp binaries
981 SUPPORT_A6 optional* support A6 DNS records
982 SUPPORT_CRYPTEQ optional support crypteq (if no auths)
983 SUPPORT_MAILDIR optional support for maildir delivery
984 SUPPORT_MAILSTORE optional support for mailstore delivery
985 SUPPORT_MBX optional support for MBX delivery
986 SUPPORT_MOVE_FROZEN_MESSAGES optional* support for frozen message moving
987 SUPPORT_PAM optional support for PAM authentication
988 SUPPORT_TLS optional support for TLS encryption over SMTP
989 SUPPORT_TRANSLATE_IP_ADDRESS optional* support for address translation
990 SYSLOG_LOG_PID optional add pid to syslog lines
991 SYSLOG_LONG_LINES optional do not split long syslog lines
992 SYSTEM_ALIASES_FILE optional defaults to /etc/aliases
993 TCP_WRAPPERS_DAEMON_NAME system* daemon name used by tcpwrappers library
994 TIMEZONE_DEFAULT optional default for timezone option
995 TLS_INCLUDE optional path to include files for TLS
996 TLS_LIBS optional additional libraries for TLS
997 EXIM_TMPDIR system value for TMPDIR environment variable
998 TRANSPORT_APPENDFILE driver include appendfile transport
999 TRANSPORT_AUTOREPLY driver include autoreply transport
1000 TRANSPORT_LMTP driver include lmtp transport
1001 TRANSPORT_PIPE driver include pipe transport
1002 TRANSPORT_SMTP driver include smtp transport
1003 TRUSTED_CONFIG_LIST optional config files safe to retain privileges
1004 USE_DB system** use native DB interface
1005 USE_GNUTLS optional use GnuTLS instead of OpenSSL
1006 USE_GNUTLS_PC optional probably "gnutls"
1007 USE_OPENSSL_PC optional probably "openssl"
1008 USE_READLINE optional try to load libreadline for -be
1009 USE_TCP_WRAPPERS system link with tcpwrappers
1010 USE_TDB optional use the tdb DB interface
1011 WHITELIST_D_MACROS optional -Dmacros safe to retain privileges with
1012 WITH_OLD_CLAMAV_STREAM optional* use ClamAV API from before ClamAV 0.95
1013 X11 system** X11 base directory
1014 X11_LD_LIB system** X11 link library
1015 XINCLUDE system** X11 include directory
1016 XLFLAGS system** X11 link time flags
1017 ZCAT_COMMAND system path to zcat command
1020 4. BUILD TIME OPTIONS FOR EXIMON
1021 --------------------------------
1023 The table below contains a complete list of options that can be set in
1024 Local/eximon.conf when building the Exim monitor. Where the default is shown as
1025 ** it means that the text string is too long to fit in the table and is instead
1026 given below. A blank default means that there is no default value.
1028 ACTION_OUTPUT=no show output for every action
1029 ACTION_QUEUE_UPDATE=yes update queue display after actions
1030 BODY_MAX=20000 maximum body display
1031 DOMAIN= domain to strip from window title
1032 LOG_BUFFER=20K buffer for log tail
1033 LOG_DEPTH=300 depth of log subwindow
1034 LOG_FONT=** font for log display
1035 LOG_STRIPCHARTS=** patterns for stripcharts
1036 LOG_WIDTH=950 width of log subwindow
1037 MENU_EVENT='Shift<Btn1Down>' keypress for menu
1038 MIN_HEIGHT=162 minimum window height
1039 MIN_WIDTH=103 minimum window width
1040 QUALIFY_DOMAIN= local domain to strip from addresses
1041 QUEUE_DEPTH=200 depth of queue subwindow
1042 QUEUE_FONT=$LOG_FONT font for queue display
1043 QUEUE_INTERVAL=300 queue refresh interval
1044 QUEUE_MAX_ADDRESSES=10 max addresses to show in queue
1045 QUEUE_STRIPCHART_NAME=queue name for queue stripchart
1046 QUEUE_WIDTH=950 width of queue subwindow
1047 SIZE_STRIPCHART= request partition size stripchart
1048 SIZE_STRIPCHART_NAME=space name for size stripchart
1049 START_SMALL=no if yes, start with small window
1050 STRIPCHART_INTERVAL=60 stripchart refresh interval
1051 TEXT_DEPTH=200 depth of text windows
1052 WINDOW_TITLE="${hostname} eximon" window title
1054 The default for LOG_FONT is
1056 LOG_FONT=-misc-fixed-medium-r-normal-*-14-140-*-*-*-*-iso8859-1
1058 and the default for LOG_STRIPCHARTS is
1060 LOG_STRIPCHARTS='/ <= /in/
1062 / => .+ R=local/local/
1063 / => .+ T=[^ ]*smtp/smtp/'
1065 That is, there are four stripcharts, named in, out, local, and smtp. The first
1066 counts message arrivals, the second counts all deliveries, the third counts
1067 deliveries where the router's name starts with "local", and the fourth counts
1068 deliveries where the transport name contains "smtp".
1070 **** End of OptionLists ****
git://git.exim.org / users / heiko / exim.git / blob