Re: Possible MX Lookup/Ordering Issue

From: Victor Duchovni (no email)
Date: Thu Nov 01 2007 - 12:13:44 EDT

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    On Thu, Nov 01, 2007 at 03:49:38PM +0000, wrote:

    > Nov 1 07:15:33 smtp-out-b postfix/cleanup[22462]: 5C6037A2683:
    > message-id=<!&!AAAAAAAAAAAYAAAAAAAAAMZwGI7IkCJPiEIFgLPzqtnCgAAAEAAAA
    > FTJx60TftpBkIoHmlwF8GsBAAAAAA==@zoom.co.uk>

    > Nov 1 07:15:33 smtp-out-b postfix/qmgr[20307]: 5C6037A2683:
    > from=<>, size=2903, nrcpt=1 (queue active)

    > Nov 1 07:16:52 smtp-out-b postfix/smtp[22405]: 5C6037A2683:
    > to=<>, relay=none, delay=81, status=deferred
    > (connect to avt15.mail.griffin.com[85.189.39.55]: No route to host)

    This shows only one connection attempt, either you don't have multiple
    MX hosts, or you log search only looks for log entries that match the
    queue id of the message, and omits other log entries that show failed
    connection attempts with no queue id. Note the delay of "81", which
    is ~79 seconds after the first "qmgr" log entry, the message spent
    79 seconds trying various MX hosts, until it finally failed.

    Your log search is incomplete.

    > The MX records for griffin.com (target domain in this case) are (done
    > from the same machine the mail log extract came from):

    > griffin.com. 8 IN MX 10 avt0.mail.griffin.com.
    > griffin.com. 8 IN MX 30 av.griffin.com.
    > griffin.com. 8 IN MX 101 avt1.mail.griffin.com.
    > griffin.com. 8 IN MX 102 avt2.mail.griffin.com.
    > griffin.com. 8 IN MX 103 avt3.mail.griffin.com.
    > griffin.com. 8 IN MX 104 avt4.mail.griffin.com.
    > griffin.com. 8 IN MX 105 avt5.mail.griffin.com.
    > griffin.com. 8 IN MX 106 avt6.mail.griffin.com.
    > griffin.com. 8 IN MX 107 avt7.mail.griffin.com.
    > griffin.com. 8 IN MX 108 avt8.mail.griffin.com.
    > griffin.com. 8 IN MX 109 avt9.mail.griffin.com.
    > griffin.com. 8 IN MX 110 avt10.mail.griffin.com.
    > griffin.com. 8 IN MX 111 avt11.mail.griffin.com.
    > griffin.com. 8 IN MX 112 avt12.mail.griffin.com.
    > griffin.com. 8 IN MX 113 avt13.mail.griffin.com.
    > griffin.com. 8 IN MX 114 avt14.mail.griffin.com.
    > griffin.com. 8 IN MX 115 avt15.mail.griffin.com.

    This is already excessive, but combined with a reportedly flakey DNS
    server, jumbo MX RRsets are rather unwise. If the full RRset fits into a
    UDP DNS response, Postfix will use traverse the MX hosts in the specified
    order, trying at most 2 sessions and at most 5 (varies with release)
    MX connection attempts to the MX hosts ordered by priority.

    Your log search is broken, so all we know for now is that your MX RRsets
    are very poorly chosen.

    -- 
    	Viktor.
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