X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/3369a853fbc0fe454ac65fef7adf7e51845ff6a2..66387a737208e277990b0cbfe58db3db419f34b2:/doc/doc-txt/experimental-spec.txt diff --git a/doc/doc-txt/experimental-spec.txt b/doc/doc-txt/experimental-spec.txt index 5213d8be4..855f9899a 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 @@ -292,183 +292,18 @@ These four steps are explained in more details below. -Sender Policy Framework (SPF) support --------------------------------------------------------------- - -To learn more about SPF, visit http://www.openspf.org. This -document does not explain the SPF fundamentals, you should -read and understand the implications of deploying SPF on your -system before doing so. - -SPF support is added via the libspf2 library. Visit - - http://www.libspf2.org/ - -to obtain a copy, then compile and install it. By default, -this will put headers in /usr/local/include and the static -library in /usr/local/lib. - -To compile Exim with SPF support, set these additional flags in -Local/Makefile: - -EXPERIMENTAL_SPF=yes -CFLAGS=-DSPF -I/usr/local/include -EXTRALIBS_EXIM=-L/usr/local/lib -lspf2 - -This assumes that the libspf2 files are installed in -their default locations. - -You can now run SPF checks in incoming SMTP by using the "spf" -ACL condition in either the MAIL, RCPT or DATA ACLs. When -using it in the RCPT ACL, you can make the checks dependent on -the RCPT address (or domain), so you can check SPF records -only for certain target domains. This gives you the -possibility to opt-out certain customers that do not want -their mail to be subject to SPF checking. - -The spf condition takes a list of strings on its right-hand -side. These strings describe the outcome of the SPF check for -which the spf condition should succeed. Valid strings are: - - o pass The SPF check passed, the sending host - is positively verified by SPF. - o fail The SPF check failed, the sending host - is NOT allowed to send mail for the domain - in the envelope-from address. - o softfail The SPF check failed, but the queried - domain can't absolutely confirm that this - is a forgery. - o none The queried domain does not publish SPF - records. - o neutral The SPF check returned a "neutral" state. - This means the queried domain has published - a SPF record, but wants to allow outside - servers to send mail under its domain as well. - This should be treated like "none". - o permerror This indicates a syntax error in the SPF - record of the queried domain. You may deny - messages when this occurs. (Changed in 4.83) - o temperror This indicates a temporary error during all - processing, including Exim's SPF processing. - You may defer messages when this occurs. - (Changed in 4.83) - o err_temp Same as permerror, deprecated in 4.83, will be - removed in a future release. - o err_perm Same as temperror, deprecated in 4.83, will be - removed in a future release. - -You can prefix each string with an exclamation mark to invert -its meaning, for example "!fail" will match all results but -"fail". The string list is evaluated left-to-right, in a -short-circuit fashion. When a string matches the outcome of -the SPF check, the condition succeeds. If none of the listed -strings matches the outcome of the SPF check, the condition -fails. - -Here is an example to fail forgery attempts from domains that -publish SPF records: - -/* ----------------- -deny message = $sender_host_address is not allowed to send mail from ${if def:sender_address_domain {$sender_address_domain}{$sender_helo_name}}. \ - Please see http://www.openspf.org/Why?scope=${if def:sender_address_domain {mfrom}{helo}};identity=${if def:sender_address_domain {$sender_address}{$sender_helo_name}};ip=$sender_host_address - spf = fail ---------------------- */ - -You can also give special treatment to specific domains: - -/* ----------------- -deny message = AOL sender, but not from AOL-approved relay. - sender_domains = aol.com - spf = fail:neutral ---------------------- */ - -Explanation: AOL publishes SPF records, but is liberal and -still allows non-approved relays to send mail from aol.com. -This will result in a "neutral" state, while mail from genuine -AOL servers will result in "pass". The example above takes -this into account and treats "neutral" like "fail", but only -for aol.com. Please note that this violates the SPF draft. - -When the spf condition has run, it sets up several expansion -variables. - - $spf_header_comment - This contains a human-readable string describing the outcome - of the SPF check. You can add it to a custom header or use - it for logging purposes. - - $spf_received - This contains a complete Received-SPF: header that can be - added to the message. Please note that according to the SPF - draft, this header must be added at the top of the header - list. Please see section 10 on how you can do this. - - Note: in case of "Best-guess" (see below), the convention is - to put this string in a header called X-SPF-Guess: instead. - - $spf_result - This contains the outcome of the SPF check in string form, - one of pass, fail, softfail, none, neutral, permerror or - temperror. - - $spf_smtp_comment - This contains a string that can be used in a SMTP response - to the calling party. Useful for "fail". - -In addition to SPF, you can also perform checks for so-called -"Best-guess". Strictly speaking, "Best-guess" is not standard -SPF, but it is supported by the same framework that enables SPF -capability. Refer to http://www.openspf.org/FAQ/Best_guess_record -for a description of what it means. - -To access this feature, simply use the spf_guess condition in place -of the spf one. For example: - -/* ----------------- -deny message = $sender_host_address doesn't look trustworthy to me - spf_guess = fail ---------------------- */ - -In case you decide to reject messages based on this check, you -should note that although it uses the same framework, "Best-guess" -is NOT SPF, and therefore you should not mention SPF at all in your -reject message. - -When the spf_guess condition has run, it sets up the same expansion -variables as when spf condition is run, described above. - -Additionally, since Best-guess is not standardized, you may redefine -what "Best-guess" means to you by redefining spf_guess variable in -global config. For example, the following: - -/* ----------------- -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 -------------------------------------------------------------- Exiscan currently includes SRS support via Miles Wilton's libsrs_alt library. The current version of the supported -library is 0.5. +library is 0.5, there are reports of 1.0 working. In order to use SRS, you must get a copy of libsrs_alt from -http://srs.mirtol.com/ +https://opsec.eu/src/srs/ + +(not the original source, which has disappeared.) Unpack the tarball, then refer to MTAs/README.EXIM to proceed. You need to set @@ -478,6 +313,7 @@ EXPERIMENTAL_SRS=yes in your Local/Makefile. + DCC Support -------------------------------------------------------------- Distributed Checksum Clearinghouse; http://www.rhyolite.com/dcc/ @@ -550,7 +386,9 @@ 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 -------------------------------------------------------------- @@ -571,7 +409,7 @@ that headers will be in /usr/local/include, and that the libraries are in /usr/local/lib. 1. To compile Exim with DMARC support, you must first enable SPF. -Please read the above section on enabling the EXPERIMENTAL_SPF +Please read the Local/Makefile comments on enabling the SUPPORT_SPF feature. You must also have DKIM support, so you cannot set the DISABLE_DKIM feature. Once both of those conditions have been met you can enable DMARC in Local/Makefile: @@ -592,12 +430,14 @@ package controlled locations (/usr/include and /usr/lib). 2. Use the following global settings to configure DMARC: -Required: +Optional: dmarc_tld_file Defines the location of a text file of valid top level domains the opendmarc library uses during domain parsing. Maintained by Mozilla, the most current version can be downloaded from a link at http://publicsuffix.org/list/. + If unset, "/etc/exim/opendmarc.tlds" (hardcoded) + is used. Optional: dmarc_history_file Defines the location of a file to log results @@ -894,7 +734,7 @@ 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 succeded using dnssec. +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. @@ -923,6 +763,8 @@ verification succeeded using DANE and "no" otherwise (only useful in combination with EXPERIMENTAL_EVENT), and a new variable $tls_out_tlsa_usage (detailed above). +Under GnuTLS, DANE is only supported from versin 3.0.0 onwards + DSN extra information @@ -960,7 +802,7 @@ 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 somtimes give extra information over the + This string sometimes give extra information over the existing (already available) Diagnostic-Code field. @@ -970,7 +812,7 @@ 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 shoul read about the feature +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.