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Article: 315
From: Quentin Campbell
Date: 2010-02-26 05:38:01 -0500
Subject: RE: milter-ahead "not a defined route, skipping"

Anthony

Would any of the following texts be more descriptive:

  rcpt_host='%s' :unable to determine host name (MX lookup required), skipping

  rcpt_host='%s' is not a destination host - MX lookup required, skipping

  rcpt_host='%s' is not an explicit destination host - MX lookup required, skipping

  rcpt_host='%s' is not a FQDN - MX lookup required, skipping

  rcpt_host='%s' is a domain name - MX lookup required, skipping

  rcpt_host='%s' is a domain name - resolution to host name by MX lookup required,
skipping


Quentin

>-----Original Message-----
>From: milters@milter.info [mailto:milters@milter.info] On Behalf Of
>Anthony Howe
>Sent: 25 February 2010 19:17
>To: [milters]
>Subject: [milters] milter-ahead "not a defined route, skipping"
>
>(I'm sending this to the list to archive this response for future
>reference by other users of milter-ahead.)
>
>On 25/02/2010 15:25, Richard Gillman whispered from the shadows...:
>> We are also getting milter-ahead messages in the logs along the lines:
>> rcpt_host='macaulay.ac.uk' is not a defined route, skipping
>
>I assume you're still using sendmail and haven't switched to postfix
>using milters (which is possible, just a little different).
>
>The "not a defined route" has always been a hard concept to explain and
>I still haven't figured out a clear way to do it, so I'll try again.
>
>There are a handful of articles in the mailing list archive:
>
>	http://www.snertsoft.info/lists/list.php?l=milters
>
>that reference this issue. Enter "not a defined route" into the search
>box (I'll eventually update my Private Wimp MLM archive interface to
>allow this in the URL).
>
>*** Please note that these articles refer to an older versions (< 1.4)
>of milter-ahead that used single letter options, instead of the longer
>descriptive names.
>
>http://www.snertsoft.info/lists/article.php?l=milters&d=2004-10&f=140
>
>http://www.snertsoft.info/lists/article.php?l=milters&d=2004-12&f=275
>
>
>Essentially when you have -mx-lookup (original historical behaviour),
>then when you see on occasion:
>
>	"rcpt_host='%s' is not a defined route, skipping"
>
>that means that the {rcpt_host} macro (based on a mailertable entry
>processed by sendmail) or an entry in call-ahead-db if being used,
>defines a "variable" destination; variable in that it requires an MX
>lookup before a next-hop host can be determined and often there is more
>than one MX possible with different preferences.
>
>In sendmail's mailertable or the call-ahead-db option the
>right-hand-side (RHS) value specifies the next-hop and can be defined in
>square brackets, [ and ], which disables the MX lookup that sendmail
>would normally do (assuming mailertable).
>
>With square brackets eg. [mx.snert.net] or [82.10.97.34] is a _defined_
>route in that an A record lookup or an explicit IP address clearly point
>to a _specific_ machine as the next-hop.
>
>Without the square brackets eg. milter.info, specifies a domain as the
>next-hop, which relies on an MX and A lookups to find a destination
>machine.
>
>When milter-ahead was original conceived, those entries in mailertable
>that had specific hosts specified in square brackets were assumed
>internal or those of well known clients. Those without the square
>brackets were assumed to be hosts that you relayed off-site to.
>
>The original intent was that call-ahead should not be done to relays,
>machines that might be less reliable destinations that probably couldn't
>answer the call-ahead correctly (and would be considered _dumb_ or
>_blind_, ie. they accepted any mail address for a domain they hosted).
>
>> which may be related to the mx-lookup option. Again, if someone could
>> advise on these that would be great.
>
>Enter mx-lookup option. When set, +mx-lookup, {rcpt_host} macro passed
>by sendmail to the milter or the RHS from call-ahead-db lookup without
>the square brackets would invoke MX and A lookups to find a host to make
>the call-ahead to.
>
>When using +mx-looklup, if the mailertable or call-ahead-db specify
>next-hop that go off-site to untrusted destinations, particularly those
>that are _dumb_ (eg. might use catch-all addresses), then you weaken the
>benefit of call-ahead with +mx-lookup.
>
>So as you can see trying to find a suitable term / phrase to explained
>all this was not easy. I opted for "defined route". Happy to hear
>alternative suggestions.
>
>--
>Anthony C Howe            Skype: SirWumpus                  SnertSoft
>+33 6 11 89 73 78       Twitter: SirWumpus      BarricadeMX & Milters
>http://snert.com/      http://nanozen.info/     http://snertsoft.com/


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