X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/a7538db17824b7fd70c12ef7561a67b85d6f247e..93134c3a5998b0c16eeafc5c743c505bce73ae50:/doc/doc-txt/experimental-spec.txt?ds=inline diff --git a/doc/doc-txt/experimental-spec.txt b/doc/doc-txt/experimental-spec.txt index b98ac7929..2a1901ade 100644 --- a/doc/doc-txt/experimental-spec.txt +++ b/doc/doc-txt/experimental-spec.txt @@ -6,7 +6,7 @@ about experimental features, all of which are unstable and liable to incompatible change. -Brightmail AntiSpam (BMI) suppport +Brightmail AntiSpam (BMI) support -------------------------------------------------------------- Brightmail AntiSpam is a commercial package. Please see @@ -42,7 +42,7 @@ These four steps are explained in more details below. 1) Adding support for BMI at compile time To compile with BMI support, you need to link Exim against - the Brighmail client SDK, consisting of a library + the Brightmail client SDK, consisting of a library (libbmiclient_single.so) and a header file (bmi_api.h). You'll also need to explicitly set a flag in the Makefile to include BMI support in the Exim binary. Both can be achieved @@ -448,6 +448,17 @@ spf_guess = v=spf1 a/16 mx/16 ptr ?all would relax host matching rules to a broader network range. +A lookup expansion is also available. It takes an email +address as the key and an IP address as the database: + + $lookup (username@domain} spf {ip.ip.ip.ip}} + +The lookup will return the same result strings as they can appear in +$spf_result (pass,fail,softfail,neutral,none,err_perm,err_temp). +Currently, only IPv4 addresses are supported. + + + SRS (Sender Rewriting Scheme) Support -------------------------------------------------------------- @@ -469,6 +480,7 @@ in your Local/Makefile. DCC Support -------------------------------------------------------------- +Distributed Checksum Clearinghouse; http://www.rhyolite.com/dcc/ *) Building exim @@ -538,7 +550,7 @@ Then set something like mout-xforward.gmx.net 82.165.159.12 mout.gmx.net 212.227.15.16 -Use a reasonable IP. eg. one the sending cluster acutally uses. +Use a reasonable IP. eg. one the sending cluster actually uses. DMARC Support -------------------------------------------------------------- @@ -623,10 +635,10 @@ exim will send these forensic emails. It's also advised that you configure a dmarc_forensic_sender because the default sender address construction might be inadequate. - control = dmarc_forensic_enable + control = dmarc_enable_forensic (AGAIN: You can choose not to send these forensic reports by simply -not putting the dmarc_forensic_enable control line at any point in +not putting the dmarc_enable_forensic control line at any point in your exim config. If you don't tell it to send them, it will not send them.) @@ -755,399 +767,307 @@ b. Configure, somewhere before the DATA ACL, the control option to deny dmarc_status = reject !authenticated = * - message = Message from $domain_used_domain failed sender's DMARC policy, REJECT - - - -Transport post-delivery actions --------------------------------------------------------------- - -An arbitrary per-transport string can be expanded on successful delivery, -and (for SMTP transports) a second string on deferrals caused by a host error. -This feature may be used, for example, to write exim internal log information -(not available otherwise) into a database. - -In order to use the feature, you must compile with - -EXPERIMENTAL_TPDA=yes - -in your Local/Makefile - -and define the tpda_event_action option in the transport, to -be expanded when the event fires. - -A new variable, $tpda_event, is set to the event type when the -expansion is done. The current list of events is: - - msg:delivery - msg:host:defer - tcp:connect - tcp:close - tls:cert - smtp:connect - -The expansion is called for all event types, and should use the $tpda_event -value to decide when to act. The variable data is a colon-separated -list, describing an event tree. - -There is an auxilary variable, $tpda_data, for which the -content is event_dependent: - - msg:delivery smtp confirmation mssage - msg:host:defer error string - tls:cert verification chain depth - smtp:connect smtp banner - -The msg:host:defer event populates one extra variable, $tpda_defer_errno. - -The following variables are likely to be useful for most event types: - - router_name, transport_name - local_part, domain - host, host_address, host_port - tls_out_peercert - lookup_dnssec_authenticated, tls_out_dane - sending_ip_address, sending_port - - -An example might look like: - -tpda_event_action = ${if = {msg:delivery}{$tpda_event} \ -{${lookup pgsql {SELECT * FROM record_Delivery( \ - '${quote_pgsql:$sender_address_domain}',\ - '${quote_pgsql:${lc:$sender_address_local_part}}', \ - '${quote_pgsql:$domain}', \ - '${quote_pgsql:${lc:$local_part}}', \ - '${quote_pgsql:$host_address}', \ - '${quote_pgsql:${lc:$host}}', \ - '${quote_pgsql:$message_exim_id}')}} \ -} {}} - -The string is expanded after the delivery completes and any -side-effects will happen. The result is then discarded. -Note that for complex operations an ACL expansion can be used. - -During the expansion the tpda_event variable will contain the -string-list "msg:delivery". - - -The expansion of the tpda_event_action option should normally -return an empty string. Should it return anything else the -following will be forced: - - msg:delivery (ignored) - msg:host:defer (ignored) - tcp:connect do not connect - tcp:close (ignored) - tls:cert refuse verification - smtp:connect close connection - + message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT + + + +DANE +------------------------------------------------------------ +DNS-based Authentication of Named Entities, as applied +to SMTP over TLS, provides assurance to a client that +it is actually talking to the server it wants to rather +than some attacker operating a Man In The Middle (MITM) +operation. The latter can terminate the TLS connection +you make, and make another one to the server (so both +you and the server still think you have an encrypted +connection) and, if one of the "well known" set of +Certificate Authorities has been suborned - something +which *has* been seen already (2014), a verifiable +certificate (if you're using normal root CAs, eg. the +Mozilla set, as your trust anchors). + +What DANE does is replace the CAs with the DNS as the +trust anchor. The assurance is limited to a) the possibility +that the DNS has been suborned, b) mistakes made by the +admins of the target server. The attack surface presented +by (a) is thought to be smaller than that of the set +of root CAs. + +It also allows the server to declare (implicitly) that +connections to it should use TLS. An MITM could simply +fail to pass on a server's STARTTLS. + +DANE scales better than having to maintain (and +side-channel communicate) copies of server certificates +for every possible target server. It also scales +(slightly) better than having to maintain on an SMTP +client a copy of the standard CAs bundle. It also +means not having to pay a CA for certificates. + +DANE requires a server operator to do three things: +1) run DNSSEC. This provides assurance to clients +that DNS lookups they do for the server have not +been tampered with. The domain MX record applying +to this server, its A record, its TLSA record and +any associated CNAME records must all be covered by +DNSSEC. +2) add TLSA DNS records. These say what the server +certificate for a TLS connection should be. +3) offer a server certificate, or certificate chain, +in TLS connections which is traceable to the one +defined by (one of?) the TSLA records + +There are no changes to Exim specific to server-side +operation of DANE. + +The TLSA record for the server may have "certificate +usage" of DANE-TA(2) or DANE-EE(3). The latter specifies +the End Entity directly, i.e. the certificate involved +is that of the server (and should be the sole one transmitted +during the TLS handshake); this is appropriate for a +single system, using a self-signed certificate. + DANE-TA usage is effectively declaring a specific CA +to be used; this might be a private CA or a public, +well-known one. A private CA at simplest is just +a self-signed certificate which is used to sign +cerver certificates, but running one securely does +require careful arrangement. If a private CA is used +then either all clients must be primed with it, or +(probably simpler) the server TLS handshake must transmit +the entire certificate chain from CA to server-certificate. +If a public CA is used then all clients must be primed with it +(losing one advantage of DANE) - but the attack surface is +reduced from all public CAs to that single CA. +DANE-TA is commonly used for several services and/or +servers, each having a TLSA query-domain CNAME record, +all of which point to a single TLSA record. + +The TLSA record should have a Selector field of SPKI(1) +and a Matching Type field of SHA2-512(2). + +At the time of writing, https://www.huque.com/bin/gen_tlsa +is useful for quickly generating TLSA records; and commands like + + openssl x509 -in -pubkey -noout /dev/null \ + | openssl sha512 \ + | awk '{print $2}' + +are workable for 4th-field hashes. + +For use with the DANE-TA model, server certificates +must have a correct name (SubjectName or SubjectAltName). + +The use of OCSP-stapling should be considered, allowing +for fast revocation of certificates (which would otherwise +be limited by the DNS TTL on the TLSA records). However, +this is likely to only be usable with DANE-TA. NOTE: the +default of requesting OCSP for all hosts is modified iff +DANE is in use, to: + + hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \ + {= {4}{$tls_out_tlsa_usage}} } \ + {*}{}} + +The (new) variable $tls_out_tlsa_usage is a bitfield with +numbered bits set for TLSA record usage codes. +The zero above means DANE was not in use, +the four means that only DANE-TA usage TLSA records were +found. If the definition of hosts_request_ocsp includes the +string "tls_out_tlsa_usage", they are re-expanded in time to +control the OCSP request. + +This modification of hosts_request_ocsp is only done if +it has the default value of "*". Admins who change it, and +those who use hosts_require_ocsp, should consider the interaction +with DANE in their OCSP settings. + + +For client-side DANE there are two new smtp transport options, +hosts_try_dane and hosts_require_dane. +[ should they be domain-based rather than host-based? ] + +Hosts_require_dane will result in failure if the target host +is not DNSSEC-secured. + +DANE will only be usable if the target host has DNSSEC-secured +MX, A and TLSA records. + +A TLSA lookup will be done if either of the above options match +and the host-lookup succeeded using dnssec. +If a TLSA lookup is done and succeeds, a DANE-verified TLS connection +will be required for the host. If it does not, the host will not +be used; there is no fallback to non-DANE or non-TLS. + +If DANE is requested and useable (see above) the following transport +options are ignored: + hosts_require_tls + tls_verify_hosts + tls_try_verify_hosts + tls_verify_certificates + tls_crl + tls_verify_cert_hostnames + +If DANE is not usable, whether requested or not, and CA-anchored +verification evaluation is wanted, the above variables should be set +appropriately. + +Currently dnssec_request_domains must be active (need to think about that) +and dnssec_require_domains is ignored. + +If verification was successful using DANE then the "CV" item +in the delivery log line will show as "CV=dane". + +There is a new variable $tls_out_dane which will have "yes" if +verification succeeded using DANE and "no" otherwise (only useful +in combination with EXPERIMENTAL_EVENT), and a new variable +$tls_out_tlsa_usage (detailed above). + + + +DSN extra information +--------------------- +If compiled with EXPERIMENTAL_DSN_INFO extra information will be added +to DSN fail messages ("bounces"), when available. The intent is to aid +tracing of specific failing messages, when presented with a "bounce" +complaint and needing to search logs. + + +The remote MTA IP address, with port number if nonstandard. +Example: + Remote-MTA: X-ip; [127.0.0.1]:587 +Rationale: + Several addresses may correspond to the (already available) + dns name for the remote MTA. + +The remote MTA connect-time greeting. +Example: + X-Remote-MTA-smtp-greeting: X-str; 220 the.local.host.name ESMTP Exim x.yz Tue, 2 Mar 1999 09:44:33 +0000 +Rationale: + This string sometimes presents the remote MTA's idea of its + own name, and sometimes identifies the MTA software. + +The remote MTA response to HELO or EHLO. +Example: + X-Remote-MTA-helo-response: X-str; 250-the.local.host.name Hello localhost [127.0.0.1] +Limitations: + Only the first line of a multiline response is recorded. +Rationale: + This string sometimes presents the remote MTA's view of + the peer IP connecting to it. + +The reporting MTA detailed diagnostic. +Example: + X-Exim-Diagnostic: X-str; SMTP error from remote mail server after RCPT TO:: 550 hard error +Rationale: + This string sometimes give extra information over the + existing (already available) Diagnostic-Code field. + + +Note that non-RFC-documented field names and data types are used. + + +LMDB Lookup support +------------------- +LMDB is an ultra-fast, ultra-compact, crash-proof key-value embedded data store. +It is modeled loosely on the BerkeleyDB API. You should read about the feature +set as well as operation modes at https://symas.com/products/lightning-memory-mapped-database/ +LMDB single key lookup support is provided by linking to the LMDB C library. +The current implementation does not support writing to the LMDB database. +Visit https://github.com/LMDB/lmdb to download the library or find it in your +operating systems package repository. - -Redis Lookup --------------------------------------------------------------- - -Redis is open source advanced key-value data store. This document -does not explain the fundamentals, you should read and understand how -it works by visiting the website at http://www.redis.io/. - -Redis lookup support is added via the hiredis library. Visit: - - https://github.com/redis/hiredis - -to obtain a copy, or find it in your operating systems package repository. If building from source, this description assumes that headers will be in /usr/local/include, and that the libraries are in /usr/local/lib. -1. In order to build exim with Redis lookup support add +1. In order to build exim with LMDB lookup support add or uncomment -EXPERIMENTAL_REDIS=yes +EXPERIMENTAL_LMDB=yes to your Local/Makefile. (Re-)build/install exim. exim -d should show -Experimental_Redis in the line "Support for:". +Experimental_LMDB in the line "Support for:". -EXPERIMENTAL_REDIS=yes -LDFLAGS += -lhiredis +EXPERIMENTAL_LMDB=yes +LDFLAGS += -llmdb # CFLAGS += -I/usr/local/include # LDFLAGS += -L/usr/local/lib The first line sets the feature to include the correct code, and -the second line says to link the hiredis libraries into the +the second line says to link the LMDB libraries into the exim binary. The commented out lines should be uncommented if you -built hiredis from source and installed in the default location. +built LMDB from source and installed in the default location. Adjust the paths if you installed them elsewhere, but you do not need to uncomment them if an rpm (or you) installed them in the package controlled locations (/usr/include and /usr/lib). +2. Create your LMDB files, you can use the mdb_load utility which is +part of the LMDB distribution our your favourite language bindings. -2. Use the following global settings to configure Redis lookup support: - -Required: -redis_servers This option provides a list of Redis servers - and associated connection data, to be used in - conjunction with redis lookups. The option is - only available if Exim is configured with Redis - support. - -For example: - -redis_servers = 127.0.0.1/10/ - using database 10 with no password -redis_servers = 127.0.0.1//password - to make use of the default database of 0 with a password -redis_servers = 127.0.0.1// - for default database of 0 with no password - -3. Once you have the Redis servers defined you can then make use of the -experimental Redis lookup by specifying ${lookup redis{}} in a lookup query. - -4. Example usage: +3. Add the single key lookups to your exim.conf file, example lookups +are below. -(Host List) -hostlist relay_from_ips = <\n ${lookup redis{SMEMBERS relay_from_ips}} +${lookup{$sender_address_domain}lmdb{/var/lib/baruwa/data/db/relaydomains.mdb}{$value}} +${lookup{$sender_address_domain}lmdb{/var/lib/baruwa/data/db/relaydomains.mdb}{$value}fail} +${lookup{$sender_address_domain}lmdb{/var/lib/baruwa/data/db/relaydomains.mdb}} -Where relay_from_ips is a Redis set which contains entries such as "192.168.0.0/24" "10.0.0.0/8" and so on. -The result set is returned as -192.168.0.0/24 -10.0.0.0/8 -.. -. -(Domain list) -domainlist virtual_domains = ${lookup redis {HGET $domain domain}} +Queuefile transport +------------------- +Queuefile is a pseudo transport which does not perform final delivery. +It simply copies the exim spool files out of the spool directory into +an external directory retaining the exim spool format. -Where $domain is a hash which includes the key 'domain' and the value '$domain'. +The spool files can then be processed by external processes and then +requeued into exim spool directories for final delivery. -(Adding or updating an existing key) -set acl_c_spammer = ${if eq{${lookup redis{SPAMMER_SET}}}{OK}} +The motivation/inspiration for the transport is to allow external +processes to access email queued by exim and have access to all the +information which would not be available if the messages were delivered +to the process in the standard email formats. -Where SPAMMER_SET is a macro and it is defined as +The mailscanner package is one of the processes that can take advantage +of this transport to filter email. -"SET SPAMMER " +The transport can be used in the same way as the other existing transports, +i.e by configuring a router to route mail to a transport configured with +the queuefile driver. -(Getting a value from Redis) +The transport only takes one option: -set acl_c_spam_host = ${lookup redis{GET...}} +* directory - This is used to specify the directory messages should be +copied to +The generic transport options (body_only, current_directory, disable_logging, +debug_print, delivery_date_add, envelope_to_add, event_action, group, +headers_add, headers_only, headers_remove, headers_rewrite, home_directory, +initgroups, max_parallel, message_size_limit, rcpt_include_affixes, +retry_use_local_part, return_path, return_path_add, shadow_condition, +shadow_transport, transport_filter, transport_filter_timeout, user) are +ignored. -Proxy Protocol Support --------------------------------------------------------------- +Sample configuration: -Exim now has Experimental "Proxy Protocol" support. It was built on -specifications from: -http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt -Above URL revised May 2014 to change version 2 spec: -http://git.1wt.eu/web?p=haproxy.git;a=commitdiff;h=afb768340c9d7e50d8e - -The purpose of this function is so that an application load balancer, -such as HAProxy, can sit in front of several Exim servers and Exim -will log the IP that is connecting to the proxy server instead of -the IP of the proxy server when it connects to Exim. It resets the -$sender_address_host and $sender_address_port to the IP:port of the -connection to the proxy. It also re-queries the DNS information for -this new IP address so that the original sender's hostname and IP -get logged in the Exim logfile. There is no logging if a host passes or -fails Proxy Protocol negotiation, but it can easily be determined and -recorded in an ACL (example is below). - -1. To compile Exim with Proxy Protocol support, put this in -Local/Makefile: +(Router) -EXPERIMENTAL_PROXY=yes - -2. Global configuration settings: - -proxy_required_hosts = HOSTLIST - -The proxy_required_hosts option will require any IP in that hostlist -to use Proxy Protocol. The specification of Proxy Protocol is very -strict, and if proxy negotiation fails, Exim will not allow any SMTP -command other than QUIT. (See end of this section for an example.) -The option is expanded when used, so it can be a hostlist as well as -string of IP addresses. Since it is expanded, specifying an alternate -separator is supported for ease of use with IPv6 addresses. - -To log the IP of the proxy in the incoming logline, add: - log_selector = +proxy - -A default incoming logline (wrapped for appearance) will look like this: - - 2013-11-04 09:25:06 1VdNti-0001OY-1V <= me@example.net - H=mail.example.net [1.2.3.4] P=esmtp S=433 - -With the log selector enabled, an email that was proxied through a -Proxy Protocol server at 192.168.1.2 will look like this: - - 2013-11-04 09:25:06 1VdNti-0001OY-1V <= me@example.net - H=mail.example.net [1.2.3.4] P=esmtp PRX=192.168.1.2 S=433 - -3. In the ACL's the following expansion variables are available. - -proxy_host_address The (internal) src IP of the proxy server - making the connection to the Exim server. -proxy_host_port The (internal) src port the proxy server is - using to connect to the Exim server. -proxy_target_address The dest (public) IP of the remote host to - the proxy server. -proxy_target_port The dest port the remote host is using to - connect to the proxy server. -proxy_session Boolean, yes/no, the connected host is required - to use Proxy Protocol. - -There is no expansion for a failed proxy session, however you can detect -it by checking if $proxy_session is true but $proxy_host is empty. As -an example, in my connect ACL, I have: - - warn condition = ${if and{ {bool{$proxy_session}} \ - {eq{$proxy_host_address}{}} } } - log_message = Failed required proxy protocol negotiation \ - from $sender_host_name [$sender_host_address] - - warn condition = ${if and{ {bool{$proxy_session}} \ - {!eq{$proxy_host_address}{}} } } - # But don't log health probes from the proxy itself - condition = ${if eq{$proxy_host_address}{$sender_host_address} \ - {false}{true}} - log_message = Successfully proxied from $sender_host_name \ - [$sender_host_address] through proxy protocol \ - host $proxy_host_address - - # Possibly more clear - warn logwrite = Remote Source Address: $sender_host_address:$sender_host_port - logwrite = Proxy Target Address: $proxy_target_address:$proxy_target_port - logwrite = Proxy Internal Address: $proxy_host_address:$proxy_host_port - logwrite = Internal Server Address: $received_ip_address:$received_port - - -4. Recommended ACL additions: - - Since the real connections are all coming from your proxy, and the - per host connection tracking is done before Proxy Protocol is - evaluated, smtp_accept_max_per_host must be set high enough to - handle all of the parallel volume you expect per inbound proxy. - - With the smtp_accept_max_per_host set so high, you lose the ability - to protect your server from massive numbers of inbound connections - from one IP. In order to prevent your server from being DOS'd, you - need to add a per connection ratelimit to your connect ACL. I - suggest something like this: - - # Set max number of connections per host - LIMIT = 5 - # Or do some kind of IP lookup in a flat file or database - # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}} - - defer message = Too many connections from this IP right now - ratelimit = LIMIT / 5s / per_conn / strict - - -5. Runtime issues to be aware of: - - The proxy has 3 seconds (hard-coded in the source code) to send the - required Proxy Protocol header after it connects. If it does not, - the response to any commands will be: - "503 Command refused, required Proxy negotiation failed" - - If the incoming connection is configured in Exim to be a Proxy - Protocol host, but the proxy is not sending the header, the banner - does not get sent until the timeout occurs. If the sending host - sent any input (before the banner), this causes a standard Exim - synchronization error (i.e. trying to pipeline before PIPELINING - was advertised). - - This is not advised, but is mentioned for completeness if you have - a specific internal configuration that you want this: If the Exim - server only has an internal IP address and no other machines in your - organization will connect to it to try to send email, you may - simply set the hostlist to "*", however, this will prevent local - mail programs from working because that would require mail from - localhost to use Proxy Protocol. Again, not advised! - -6. Example of a refused connection because the Proxy Protocol header was -not sent from a host configured to use Proxy Protocol. In the example, -the 3 second timeout occurred (when a Proxy Protocol banner should have -been sent), the banner was displayed to the user, but all commands are -rejected except for QUIT: - -# nc mail.example.net 25 -220-mail.example.net, ESMTP Exim 4.82+proxy, Mon, 04 Nov 2013 10:45:59 -220 -0800 RFC's enforced -EHLO localhost -503 Command refused, required Proxy negotiation failed -QUIT -221 mail.example.net closing connection - - -DSN Support --------------------------------------------------------------- +scan: + driver = accept + transport = scan -DSN Support tries to add RFC 3461 support to Exim. It adds support for -*) the additional parameters for MAIL FROM and RCPT TO -*) RFC complient MIME DSN messages for all of - success, failure and delay notifications -*) dsn_advertise_hosts main option to select which hosts are able - to use the extension -*) dsn_lasthop router switch to end DSN processing +(Transport) -In case of failure reports this means that the last three parts, the message body -intro, size info and final text, of the defined template are ignored since there is no -logical place to put them in the MIME message. +scan: + driver = queuefile + directory = /var/spool/baruwa-scanner/input -All the other changes are made without changing any defaults -Building exim: --------------- +In order to build exim with Queuefile transport support add or uncomment -Define -EXPERIMENTAL_DSN=YES -in your Local/Makefile. - -Configuration: --------------- -All DSNs are sent in MIME format if you built exim with EXPERIMENTAL_DSN=YES -No option needed to activate it, and no way to turn it off. - -Failure and delay DSNs are triggered as usual except a sender used NOTIFY=... -to prevent them. - -Support for Success DSNs is added and activated by NOTIFY=SUCCESS by clients. - -Add -dsn_advertise_hosts = * -or a more restrictive host_list to announce DSN in EHLO answers - -Those hosts can then use NOTIFY,ENVID,RET,ORCPT options. - -If a message is relayed to a DSN aware host without changing the envelope -recipient the options are passed along and no success DSN is generated. - -A redirect router will always trigger a success DSN if requested and the DSN -options are not passed any further. - -A success DSN always contains the recipient address as submitted by the -client as required by RFC. Rewritten addresses are never exposed. - -If you used DSN patch up to 1.3 before remove all "dsn_process" switches from -your routers since you don't need them anymore. There is no way to "gag" -success DSNs anymore. Announcing DSN means answering as requested. - -You can prevent Exim from passing DSN options along to other DSN aware hosts by defining -dsn_lasthop -in a router. Exim will then send the success DSN himself if requested as if -the next hop does not support DSN. -Adding it to a redirect router makes no difference. - -Certificate name checking --------------------------------------------------------------- -The X509 certificates used for TLS are supposed be verified -that they are owned by the expected host. The coding of TLS -support to date has not made these checks. - -If built with EXPERIMENTAL_CERTNAMES defined, code is -included to do so, and a new smtp transport option -"tls_verify_cert_hostname" supported which takes a list of -names for which the checks must be made. The host must -also be in "tls_verify_hosts". - -Both Subject and Subject-Alternate-Name certificate fields -are supported, as are wildcard certificates (limited to -a single wildcard being the initial component of a 3-or-more -component FQDN). +EXPERIMENTAL_QUEUEFILE=yes +to your Local/Makefile. (Re-)build/install exim. exim -d should show +Experimental_QUEUEFILE in the line "Support for:". --------------------------------------------------------------