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7bafa7d9 TK |
1 | From time to time, experimental features may be added to Exim. |
2 | While a feature is experimental, there will be a build-time | |
3 | option whose name starts "EXPERIMENTAL_" that must be set in | |
4 | order to include the feature. This file contains information | |
5 | about experimenatal features, all of which are unstable and | |
ee161e8f PH |
6 | liable to incompatibile change. |
7 | ||
8 | ||
3f7eeb86 PP |
9 | OCSP Stapling support |
10 | -------------------------------------------------------------- | |
11 | ||
12 | X509 PKI certificates expire and can be revoked; to handle this, the | |
13 | clients need some way to determine if a particular certificate, from a | |
14 | particular Certificate Authority (CA), is still valid. There are three | |
15 | main ways to do so. | |
16 | ||
17 | The simplest way is to serve up a Certificate Revocation List (CRL) with | |
18 | an ordinary web-server, regenerating the CRL before it expires. The | |
19 | downside is that clients have to periodically re-download a potentially | |
20 | huge file from every certificate authority it knows of. | |
21 | ||
22 | The way with most moving parts at query time is Online Certificate | |
23 | Status Protocol (OCSP), where the client verifies the certificate | |
24 | against an OCSP server run by the CA. This lets the CA track all | |
25 | usage of the certs. This requires running software with access to the | |
26 | private key of the CA, to sign the responses to the OCSP queries. OCSP | |
27 | is based on HTTP and can be proxied accordingly. | |
28 | ||
29 | The only widespread OCSP server implementation (known to this writer) | |
30 | comes as part of OpenSSL and aborts on an invalid request, such as | |
31 | connecting to the port and then disconnecting. This requires | |
32 | re-entering the passphrase each time some random client does this. | |
33 | ||
34 | The third way is OCSP Stapling; in this, the server using a certificate | |
35 | issued by the CA periodically requests an OCSP proof of validity from | |
36 | the OCSP server, then serves it up inline as part of the TLS | |
37 | negotiation. This approach adds no extra round trips, does not let the | |
38 | CA track users, scales well with number of certs issued by the CA and is | |
39 | resilient to temporary OCSP server failures, as long as the server | |
40 | starts retrying to fetch an OCSP proof some time before its current | |
41 | proof expires. The downside is that it requires server support. | |
42 | ||
43 | If Exim is built with EXPERIMENTAL_OCSP and it was built with OpenSSL, | |
44 | then it gains one new option: "tls_ocsp_file". | |
45 | ||
46 | The file specified therein is expected to be in DER format, and contain | |
47 | an OCSP proof. Exim will serve it as part of the TLS handshake. This | |
48 | option will be re-expanded for SNI, if the tls_certificate option | |
49 | contains $tls_sni, as per other TLS options. | |
50 | ||
51 | Exim does not at this time implement any support for fetching a new OCSP | |
52 | proof. The burden is on the administrator to handle this, outside of | |
53 | Exim. The file specified should be replaced atomically, so that the | |
54 | contents are always valid. Exim will expand the "tls_ocsp_file" option | |
55 | on each connection, so a new file will be handled transparently on the | |
56 | next connection. | |
57 | ||
58 | Exim will check for a validity next update timestamp in the OCSP proof; | |
59 | if not present, or if the proof has expired, it will be ignored. | |
60 | ||
61 | At this point in time, we're gathering feedback on use, to determine if | |
62 | it's worth adding complexity to the Exim daemon to periodically re-fetch | |
63 | OCSP files and somehow handling multiple files. | |
64 | ||
65 | ||
66 | ||
67 | ||
0b23848a | 68 | Brightmail AntiSpam (BMI) suppport |
ee161e8f PH |
69 | -------------------------------------------------------------- |
70 | ||
71 | Brightmail AntiSpam is a commercial package. Please see | |
72 | http://www.brightmail.com for more information on | |
73 | the product. For the sake of clarity, we'll refer to it as | |
74 | "BMI" from now on. | |
75 | ||
76 | ||
77 | 0) BMI concept and implementation overview | |
78 | ||
79 | In contrast to how spam-scanning with SpamAssassin is | |
80 | implemented in exiscan-acl, BMI is more suited for per | |
81 | -recipient scanning of messages. However, each messages is | |
82 | scanned only once, but multiple "verdicts" for multiple | |
83 | recipients can be returned from the BMI server. The exiscan | |
84 | implementation passes the message to the BMI server just | |
85 | before accepting it. It then adds the retrieved verdicts to | |
86 | the messages header file in the spool. These verdicts can then | |
87 | be queried in routers, where operation is per-recipient | |
88 | instead of per-message. To use BMI, you need to take the | |
89 | following steps: | |
90 | ||
91 | 1) Compile Exim with BMI support | |
3ec3e3bb | 92 | 2) Set up main BMI options (top section of Exim config file) |
ee161e8f PH |
93 | 3) Set up ACL control statement (ACL section of the config |
94 | file) | |
95 | 4) Set up your routers to use BMI verdicts (routers section | |
96 | of the config file). | |
97 | 5) (Optional) Set up per-recipient opt-in information. | |
98 | ||
8ff3788c | 99 | These four steps are explained in more details below. |
ee161e8f PH |
100 | |
101 | 1) Adding support for BMI at compile time | |
102 | ||
103 | To compile with BMI support, you need to link Exim against | |
104 | the Brighmail client SDK, consisting of a library | |
105 | (libbmiclient_single.so) and a header file (bmi_api.h). | |
106 | You'll also need to explicitly set a flag in the Makefile to | |
107 | include BMI support in the Exim binary. Both can be achieved | |
108 | with these lines in Local/Makefile: | |
109 | ||
110 | EXPERIMENTAL_BRIGHTMAIL=yes | |
47bbda99 | 111 | CFLAGS=-I/path/to/the/dir/with/the/includefile |
ee161e8f | 112 | EXTRALIBS_EXIM=-L/path/to/the/dir/with/the/library -lbmiclient_single |
8ff3788c | 113 | |
ee161e8f PH |
114 | If you use other CFLAGS or EXTRALIBS_EXIM settings then |
115 | merge the content of these lines with them. | |
116 | ||
7c0c8547 | 117 | Note for BMI6.x users: You'll also have to add -lxml2_single |
ee161e8f PH |
118 | to the EXTRALIBS_EXIM line. Users of 5.5x do not need to do |
119 | this. | |
8ff3788c | 120 | |
ee161e8f PH |
121 | You should also include the location of |
122 | libbmiclient_single.so in your dynamic linker configuration | |
123 | file (usually /etc/ld.so.conf) and run "ldconfig" | |
124 | afterwards, or else the produced Exim binary will not be | |
125 | able to find the library file. | |
126 | ||
127 | ||
3ec3e3bb | 128 | 2) Setting up BMI support in the Exim main configuration |
ee161e8f | 129 | |
3ec3e3bb | 130 | To enable BMI support in the main Exim configuration, you |
ee161e8f PH |
131 | should set the path to the main BMI configuration file with |
132 | the "bmi_config_file" option, like this: | |
8ff3788c | 133 | |
ee161e8f | 134 | bmi_config_file = /opt/brightmail/etc/brightmail.cfg |
8ff3788c | 135 | |
3ec3e3bb | 136 | This must go into section 1 of Exim's configuration file (You |
ee161e8f PH |
137 | can put it right on top). If you omit this option, it |
138 | defaults to /opt/brightmail/etc/brightmail.cfg. | |
139 | ||
140 | Note for BMI6.x users: This file is in XML format in V6.xx | |
141 | and its name is /opt/brightmail/etc/bmiconfig.xml. So BMI | |
142 | 6.x users MUST set the bmi_config_file option. | |
8ff3788c | 143 | |
ee161e8f PH |
144 | |
145 | 3) Set up ACL control statement | |
146 | ||
147 | To optimize performance, it makes sense only to process | |
148 | messages coming from remote, untrusted sources with the BMI | |
149 | server. To set up a messages for processing by the BMI | |
150 | server, you MUST set the "bmi_run" control statement in any | |
151 | ACL for an incoming message. You will typically do this in | |
152 | an "accept" block in the "acl_check_rcpt" ACL. You should | |
153 | use the "accept" block(s) that accept messages from remote | |
154 | servers for your own domain(s). Here is an example that uses | |
3ec3e3bb | 155 | the "accept" blocks from Exim's default configuration file: |
8ff3788c | 156 | |
ee161e8f PH |
157 | |
158 | accept domains = +local_domains | |
159 | endpass | |
160 | verify = recipient | |
161 | control = bmi_run | |
162 | ||
163 | accept domains = +relay_to_domains | |
164 | endpass | |
165 | verify = recipient | |
166 | control = bmi_run | |
8ff3788c | 167 | |
ee161e8f PH |
168 | If bmi_run is not set in any ACL during reception of the |
169 | message, it will NOT be passed to the BMI server. | |
170 | ||
171 | ||
172 | 4) Setting up routers to use BMI verdicts | |
173 | ||
174 | When a message has been run through the BMI server, one or | |
175 | more "verdicts" are present. Different recipients can have | |
176 | different verdicts. Each recipient is treated individually | |
177 | during routing, so you can query the verdicts by recipient | |
3ec3e3bb | 178 | at that stage. From Exim's view, a verdict can have the |
ee161e8f | 179 | following outcomes: |
8ff3788c | 180 | |
ee161e8f PH |
181 | o deliver the message normally |
182 | o deliver the message to an alternate location | |
183 | o do not deliver the message | |
8ff3788c | 184 | |
ee161e8f PH |
185 | To query the verdict for a recipient, the implementation |
186 | offers the following tools: | |
8ff3788c TK |
187 | |
188 | ||
ee161e8f PH |
189 | - Boolean router preconditions. These can be used in any |
190 | router. For a simple implementation of BMI, these may be | |
191 | all that you need. The following preconditions are | |
192 | available: | |
8ff3788c | 193 | |
ee161e8f | 194 | o bmi_deliver_default |
8ff3788c | 195 | |
ee161e8f PH |
196 | This precondition is TRUE if the verdict for the |
197 | recipient is to deliver the message normally. If the | |
198 | message has not been processed by the BMI server, this | |
199 | variable defaults to TRUE. | |
8ff3788c | 200 | |
ee161e8f | 201 | o bmi_deliver_alternate |
8ff3788c | 202 | |
ee161e8f PH |
203 | This precondition is TRUE if the verdict for the |
204 | recipient is to deliver the message to an alternate | |
205 | location. You can get the location string from the | |
206 | $bmi_alt_location expansion variable if you need it. See | |
207 | further below. If the message has not been processed by | |
208 | the BMI server, this variable defaults to FALSE. | |
8ff3788c | 209 | |
ee161e8f | 210 | o bmi_dont_deliver |
8ff3788c | 211 | |
ee161e8f PH |
212 | This precondition is TRUE if the verdict for the |
213 | recipient is NOT to deliver the message to the | |
214 | recipient. You will typically use this precondition in a | |
215 | top-level blackhole router, like this: | |
8ff3788c | 216 | |
ee161e8f PH |
217 | # don't deliver messages handled by the BMI server |
218 | bmi_blackhole: | |
219 | driver = redirect | |
220 | bmi_dont_deliver | |
221 | data = :blackhole: | |
8ff3788c | 222 | |
ee161e8f PH |
223 | This router should be on top of all others, so messages |
224 | that should not be delivered do not reach other routers | |
225 | at all. If the message has not been processed by | |
226 | the BMI server, this variable defaults to FALSE. | |
8ff3788c TK |
227 | |
228 | ||
ee161e8f PH |
229 | - A list router precondition to query if rules "fired" on |
230 | the message for the recipient. Its name is "bmi_rule". You | |
231 | use it by passing it a colon-separated list of rule | |
232 | numbers. You can use this condition to route messages that | |
233 | matched specific rules. Here is an example: | |
8ff3788c | 234 | |
ee161e8f PH |
235 | # special router for BMI rule #5, #8 and #11 |
236 | bmi_rule_redirect: | |
237 | driver = redirect | |
238 | bmi_rule = 5:8:11 | |
239 | data = postmaster@mydomain.com | |
8ff3788c TK |
240 | |
241 | ||
ee161e8f PH |
242 | - Expansion variables. Several expansion variables are set |
243 | during routing. You can use them in custom router | |
244 | conditions, for example. The following variables are | |
245 | available: | |
8ff3788c | 246 | |
ee161e8f | 247 | o $bmi_base64_verdict |
8ff3788c | 248 | |
ee161e8f PH |
249 | This variable will contain the BASE64 encoded verdict |
250 | for the recipient being routed. You can use it to add a | |
251 | header to messages for tracking purposes, for example: | |
8ff3788c | 252 | |
ee161e8f PH |
253 | localuser: |
254 | driver = accept | |
255 | check_local_user | |
256 | headers_add = X-Brightmail-Verdict: $bmi_base64_verdict | |
257 | transport = local_delivery | |
8ff3788c | 258 | |
ee161e8f PH |
259 | If there is no verdict available for the recipient being |
260 | routed, this variable contains the empty string. | |
8ff3788c | 261 | |
ee161e8f | 262 | o $bmi_base64_tracker_verdict |
8ff3788c | 263 | |
ee161e8f PH |
264 | This variable will contain a BASE64 encoded subset of |
265 | the verdict information concerning the "rules" that | |
266 | fired on the message. You can add this string to a | |
267 | header, commonly named "X-Brightmail-Tracker". Example: | |
8ff3788c | 268 | |
ee161e8f PH |
269 | localuser: |
270 | driver = accept | |
271 | check_local_user | |
272 | headers_add = X-Brightmail-Tracker: $bmi_base64_tracker_verdict | |
273 | transport = local_delivery | |
8ff3788c | 274 | |
ee161e8f PH |
275 | If there is no verdict available for the recipient being |
276 | routed, this variable contains the empty string. | |
8ff3788c | 277 | |
ee161e8f | 278 | o $bmi_alt_location |
8ff3788c | 279 | |
ee161e8f PH |
280 | If the verdict is to redirect the message to an |
281 | alternate location, this variable will contain the | |
282 | alternate location string returned by the BMI server. In | |
283 | its default configuration, this is a header-like string | |
284 | that can be added to the message with "headers_add". If | |
285 | there is no verdict available for the recipient being | |
286 | routed, or if the message is to be delivered normally, | |
287 | this variable contains the empty string. | |
8ff3788c | 288 | |
ee161e8f | 289 | o $bmi_deliver |
8ff3788c | 290 | |
ee161e8f PH |
291 | This is an additional integer variable that can be used |
292 | to query if the message should be delivered at all. You | |
293 | should use router preconditions instead if possible. | |
8ff3788c | 294 | |
ee161e8f PH |
295 | $bmi_deliver is '0': the message should NOT be delivered. |
296 | $bmi_deliver is '1': the message should be delivered. | |
8ff3788c TK |
297 | |
298 | ||
ee161e8f PH |
299 | IMPORTANT NOTE: Verdict inheritance. |
300 | The message is passed to the BMI server during message | |
301 | reception, using the target addresses from the RCPT TO: | |
302 | commands in the SMTP transaction. If recipients get expanded | |
303 | or re-written (for example by aliasing), the new address(es) | |
304 | inherit the verdict from the original address. This means | |
305 | that verdicts also apply to all "child" addresses generated | |
306 | from top-level addresses that were sent to the BMI server. | |
8ff3788c TK |
307 | |
308 | ||
ee161e8f PH |
309 | 5) Using per-recipient opt-in information (Optional) |
310 | ||
311 | The BMI server features multiple scanning "profiles" for | |
312 | individual recipients. These are usually stored in a LDAP | |
313 | server and are queried by the BMI server itself. However, | |
314 | you can also pass opt-in data for each recipient from the | |
315 | MTA to the BMI server. This is particularly useful if you | |
3ec3e3bb | 316 | already look up recipient data in Exim anyway (which can |
ee161e8f PH |
317 | also be stored in a SQL database or other source). This |
318 | implementation enables you to pass opt-in data to the BMI | |
319 | server in the RCPT ACL. This works by setting the | |
320 | 'bmi_optin' modifier in a block of that ACL. If should be | |
321 | set to a list of comma-separated strings that identify the | |
322 | features which the BMI server should use for that particular | |
323 | recipient. Ideally, you would use the 'bmi_optin' modifier | |
324 | in the same ACL block where you set the 'bmi_run' control | |
325 | flag. Here is an example that will pull opt-in data for each | |
326 | recipient from a flat file called | |
327 | '/etc/exim/bmi_optin_data'. | |
8ff3788c | 328 | |
ee161e8f | 329 | The file format: |
8ff3788c | 330 | |
ee161e8f PH |
331 | user1@mydomain.com: <OPTIN STRING1>:<OPTIN STRING2> |
332 | user2@thatdomain.com: <OPTIN STRING3> | |
8ff3788c TK |
333 | |
334 | ||
ee161e8f | 335 | The example: |
8ff3788c | 336 | |
ee161e8f PH |
337 | accept domains = +relay_to_domains |
338 | endpass | |
339 | verify = recipient | |
340 | bmi_optin = ${lookup{$local_part@$domain}lsearch{/etc/exim/bmi_optin_data}} | |
8ff3788c TK |
341 | control = bmi_run |
342 | ||
ee161e8f | 343 | Of course, you can also use any other lookup method that |
3ec3e3bb | 344 | Exim supports, including LDAP, Postgres, MySQL, Oracle etc., |
ee161e8f PH |
345 | as long as the result is a list of colon-separated opt-in |
346 | strings. | |
8ff3788c | 347 | |
ee161e8f PH |
348 | For a list of available opt-in strings, please contact your |
349 | Brightmail representative. | |
ee161e8f | 350 | |
8ff3788c TK |
351 | |
352 | ||
353 | ||
0b23848a | 354 | Sender Policy Framework (SPF) support |
ee161e8f PH |
355 | -------------------------------------------------------------- |
356 | ||
f413481d | 357 | To learn more about SPF, visit http://www.openspf.org. This |
ee161e8f PH |
358 | document does not explain the SPF fundamentals, you should |
359 | read and understand the implications of deploying SPF on your | |
360 | system before doing so. | |
361 | ||
8ff3788c | 362 | SPF support is added via the libspf2 library. Visit |
ee161e8f PH |
363 | |
364 | http://www.libspf2.org/ | |
8ff3788c | 365 | |
ee161e8f PH |
366 | to obtain a copy, then compile and install it. By default, |
367 | this will put headers in /usr/local/include and the static | |
368 | library in /usr/local/lib. | |
369 | ||
3ec3e3bb | 370 | To compile Exim with SPF support, set these additional flags in |
ee161e8f PH |
371 | Local/Makefile: |
372 | ||
373 | EXPERIMENTAL_SPF=yes | |
374 | CFLAGS=-DSPF -I/usr/local/include | |
375 | EXTRALIBS_EXIM=-L/usr/local/lib -lspf2 | |
376 | ||
377 | This assumes that the libspf2 files are installed in | |
378 | their default locations. | |
379 | ||
380 | You can now run SPF checks in incoming SMTP by using the "spf" | |
381 | ACL condition in either the MAIL, RCPT or DATA ACLs. When | |
382 | using it in the RCPT ACL, you can make the checks dependend on | |
383 | the RCPT address (or domain), so you can check SPF records | |
384 | only for certain target domains. This gives you the | |
385 | possibility to opt-out certain customers that do not want | |
386 | their mail to be subject to SPF checking. | |
387 | ||
388 | The spf condition takes a list of strings on its right-hand | |
389 | side. These strings describe the outcome of the SPF check for | |
390 | which the spf condition should succeed. Valid strings are: | |
391 | ||
392 | o pass The SPF check passed, the sending host | |
393 | is positively verified by SPF. | |
394 | o fail The SPF check failed, the sending host | |
395 | is NOT allowed to send mail for the domain | |
396 | in the envelope-from address. | |
397 | o softfail The SPF check failed, but the queried | |
398 | domain can't absolutely confirm that this | |
399 | is a forgery. | |
400 | o none The queried domain does not publish SPF | |
401 | records. | |
402 | o neutral The SPF check returned a "neutral" state. | |
403 | This means the queried domain has published | |
404 | a SPF record, but wants to allow outside | |
405 | servers to send mail under its domain as well. | |
406 | o err_perm This indicates a syntax error in the SPF | |
407 | record of the queried domain. This should be | |
408 | treated like "none". | |
409 | o err_temp This indicates a temporary error during all | |
3ec3e3bb | 410 | processing, including Exim's SPF processing. |
ee161e8f | 411 | You may defer messages when this occurs. |
8ff3788c | 412 | |
ee161e8f PH |
413 | You can prefix each string with an exclamation mark to invert |
414 | is meaning, for example "!fail" will match all results but | |
415 | "fail". The string list is evaluated left-to-right, in a | |
416 | short-circuit fashion. When a string matches the outcome of | |
417 | the SPF check, the condition succeeds. If none of the listed | |
418 | strings matches the outcome of the SPF check, the condition | |
419 | fails. | |
420 | ||
f413481d TK |
421 | Here is an example to fail forgery attempts from domains that |
422 | publish SPF records: | |
ee161e8f PH |
423 | |
424 | /* ----------------- | |
f413481d TK |
425 | deny message = $sender_host_address is not allowed to send mail from ${if def:sender_address_domain {$sender_address_domain}{$sender_helo_name}}. \ |
426 | Please see http://www.openspf.org/Why?scope=${if def:sender_address_domain {mfrom}{helo}};identity=${if def:sender_address_domain {$sender_address}{$sender_helo_name}};ip=$sender_host_address | |
ee161e8f PH |
427 | spf = fail |
428 | --------------------- */ | |
429 | ||
430 | You can also give special treatment to specific domains: | |
431 | ||
432 | /* ----------------- | |
433 | deny message = AOL sender, but not from AOL-approved relay. | |
434 | sender_domains = aol.com | |
435 | spf = fail:neutral | |
436 | --------------------- */ | |
437 | ||
438 | Explanation: AOL publishes SPF records, but is liberal and | |
439 | still allows non-approved relays to send mail from aol.com. | |
440 | This will result in a "neutral" state, while mail from genuine | |
441 | AOL servers will result in "pass". The example above takes | |
442 | this into account and treats "neutral" like "fail", but only | |
443 | for aol.com. Please note that this violates the SPF draft. | |
444 | ||
445 | When the spf condition has run, it sets up several expansion | |
446 | variables. | |
447 | ||
448 | $spf_header_comment | |
449 | This contains a human-readable string describing the outcome | |
450 | of the SPF check. You can add it to a custom header or use | |
451 | it for logging purposes. | |
8ff3788c | 452 | |
ee161e8f | 453 | $spf_received |
8fe685ad | 454 | This contains a complete Received-SPF: header that can be |
ee161e8f PH |
455 | added to the message. Please note that according to the SPF |
456 | draft, this header must be added at the top of the header | |
457 | list. Please see section 10 on how you can do this. | |
8ff3788c | 458 | |
65a7d8c3 NM |
459 | Note: in case of "Best-guess" (see below), the convention is |
460 | to put this string in a header called X-SPF-Guess: instead. | |
461 | ||
ee161e8f PH |
462 | $spf_result |
463 | This contains the outcome of the SPF check in string form, | |
464 | one of pass, fail, softfail, none, neutral, err_perm or | |
465 | err_temp. | |
8ff3788c | 466 | |
ee161e8f PH |
467 | $spf_smtp_comment |
468 | This contains a string that can be used in a SMTP response | |
469 | to the calling party. Useful for "fail". | |
8ff3788c | 470 | |
65a7d8c3 NM |
471 | In addition to SPF, you can also perform checks for so-called |
472 | "Best-guess". Strictly speaking, "Best-guess" is not standard | |
473 | SPF, but it is supported by the same framework that enables SPF | |
474 | capability. Refer to http://www.openspf.org/FAQ/Best_guess_record | |
475 | for a description of what it means. | |
476 | ||
477 | To access this feature, simply use the spf_guess condition in place | |
478 | of the spf one. For example: | |
479 | ||
480 | /* ----------------- | |
481 | deny message = $sender_host_address doesn't look trustworthy to me | |
482 | spf_guess = fail | |
483 | --------------------- */ | |
484 | ||
485 | In case you decide to reject messages based on this check, you | |
486 | should note that although it uses the same framework, "Best-guess" | |
487 | is NOT SPF, and therefore you should not mention SPF at all in your | |
488 | reject message. | |
489 | ||
490 | When the spf_guess condition has run, it sets up the same expansion | |
491 | variables as when spf condition is run, described above. | |
492 | ||
493 | Additionally, since Best-guess is not standarized, you may redefine | |
494 | what "Best-guess" means to you by redefining spf_guess variable in | |
495 | global config. For example, the following: | |
496 | ||
497 | /* ----------------- | |
498 | spf_guess = v=spf1 a/16 mx/16 ptr ?all | |
499 | --------------------- */ | |
500 | ||
501 | would relax host matching rules to a broader network range. | |
8ff3788c | 502 | |
ee161e8f | 503 | |
0b23848a | 504 | SRS (Sender Rewriting Scheme) Support |
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505 | -------------------------------------------------------------- |
506 | ||
507 | Exiscan currently includes SRS support via Miles Wilton's | |
8ff3788c | 508 | libsrs_alt library. The current version of the supported |
ee161e8f PH |
509 | library is 0.5. |
510 | ||
511 | In order to use SRS, you must get a copy of libsrs_alt from | |
512 | ||
513 | http://srs.mirtol.com/ | |
514 | ||
515 | Unpack the tarball, then refer to MTAs/README.EXIM | |
516 | to proceed. You need to set | |
517 | ||
518 | EXPERIMENTAL_SRS=yes | |
519 | ||
520 | in your Local/Makefile. | |
521 | ||
522 | ||
0e1ccf44 PP |
523 | DCC Support |
524 | -------------------------------------------------------------- | |
525 | ||
526 | *) Building exim | |
527 | ||
528 | In order to build exim with DCC support add | |
529 | ||
530 | EXPERIMENTAL_DCC=yes | |
531 | ||
532 | to your Makefile. (Re-)build/install exim. exim -d should show | |
533 | EXPERIMENTAL_DCC under "Support for". | |
534 | ||
535 | ||
536 | *) Configuration | |
537 | ||
538 | In the main section of exim.cf add at least | |
539 | dccifd_address = /usr/local/dcc/var/dccifd | |
540 | or | |
541 | dccifd_address = <ip> <port> | |
542 | ||
543 | In the DATA ACL you can use the new condition | |
544 | dcc = * | |
545 | ||
546 | After that "$dcc_header" contains the X-DCC-Header. | |
547 | ||
548 | Returnvalues are: | |
549 | fail for overall "R", "G" from dccifd | |
550 | defer for overall "T" from dccifd | |
551 | accept for overall "A", "S" from dccifd | |
552 | ||
553 | dcc = */defer_ok works as for spamd. | |
554 | ||
555 | The "$dcc_result" variable contains the overall result from DCC | |
556 | answer. There will an X-DCC: header added to the mail. | |
557 | ||
558 | Usually you'll use | |
559 | defer !dcc = * | |
560 | to greylist with DCC. | |
561 | ||
562 | If you set, in the main section, | |
563 | dcc_direct_add_header = true | |
564 | then the dcc header will be added "in deep" and if the spool | |
565 | file was already written it gets removed. This forces Exim to | |
566 | write it again if needed. This helps to get the DCC Header | |
567 | through to eg. SpamAssassin. | |
568 | ||
569 | If you want to pass even more headers in the middle of the | |
570 | DATA stage you can set | |
571 | $acl_m_dcc_add_header | |
572 | to tell the DCC routines add more information; eg, you might set | |
573 | this to some results from ClamAV. Be careful. Header syntax is | |
574 | not checked and is added "as is". | |
575 | ||
576 | ||
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577 | -------------------------------------------------------------- |
578 | End of file | |
579 | -------------------------------------------------------------- |