I have a RHEL5 machine running Redhat's build of postfix 2.3.3 and am having problems with messages being sporadically deferred with 'unknown mail transport error'.
The machine is a gateway for listserv, so it does receive lots of mail at times. It appears that the problem is related to the amount of mail being queued - if I do a postqueue -f, most of the problem messages are again deferred with the same error. If I slowly put the back onto the queue with postsuper -r <qid> ; sleep 1 then most messages flow through without any problems. I've done some debugging - postfix appears to be successfully looking up the user in LDAP and getting a mailhost, but fails before it opens an smtp connection to the mailhost. Here's some verbose output from qmgr: Sep 30 20:22:18 jay postfix/qmgr[10510]: send attr address = <user1>@DREXEL.EDU Sep 30 20:22:18 jay postfix/qmgr[10510]: private/rewrite socket: wanted attribute: flags Sep 30 20:22:18 jay postfix/qmgr[10510]: input attribute name: flags Sep 30 20:22:18 jay postfix/qmgr[10510]: input attribute value: 0 Sep 30 20:22:18 jay postfix/qmgr[10510]: private/rewrite socket: wanted attribute: transport Sep 30 20:22:18 jay postfix/qmgr[10510]: input attribute name: transport Sep 30 20:22:18 jay postfix/qmgr[10510]: input attribute value: smtp Sep 30 20:22:18 jay postfix/qmgr[10510]: private/rewrite socket: wanted attribute: nexthop Sep 30 20:22:18 jay postfix/qmgr[10510]: input attribute name: nexthop Sep 30 20:22:18 jay postfix/qmgr[10510]: input attribute value: [<mailhost>.irt.drexel.edu] Sep 30 20:22:18 jay postfix/qmgr[10510]: private/rewrite socket: wanted attribute: recipient Sep 30 20:22:18 jay postfix/qmgr[10510]: input attribute name: recipient Sep 30 20:22:18 jay postfix/qmgr[10510]: input attribute value: <user1>@DREXEL.EDU Sep 30 20:22:18 jay postfix/qmgr[10510]: private/rewrite socket: wanted attribute: flags Sep 30 20:22:18 jay postfix/qmgr[10510]: input attribute name: flags Sep 30 20:22:18 jay postfix/qmgr[10510]: input attribute value: 4096 Sep 30 20:22:18 jay postfix/qmgr[10510]: private/rewrite socket: wanted attribute: (list terminator) Sep 30 20:22:18 jay postfix/qmgr[10510]: input attribute name: (end) Sep 30 20:22:18 jay postfix/qmgr[10510]: resolve_clnt: `owner-drexel-official-students-al...@lists.drexel.edu' -> `<user1>@DREXEL.EDU' -> transp=`smtp' host=`[<mailhost>.irt.drexel.edu]' rcpt=`<user1>@DREXEL.EDU' flags= class=default Sep 30 20:22:18 jay postfix/qmgr[10510]: start sorted recipient list Sep 30 20:22:18 jay postfix/qmgr[10510]: qmgr_message_sort: <user1>@DREXEL.EDU Sep 30 20:22:18 jay postfix/qmgr[10510]: qmgr_message_sort: <user2>@DREXEL.EDU Sep 30 20:22:18 jay postfix/qmgr[10510]: end sorted recipient list Sep 30 20:22:18 jay postfix/qmgr[10510]: private/smtp socket: wanted attribute: status Sep 30 20:22:18 jay postfix/qmgr[10510]: warning: premature end-of-input on private/smtp socket while reading input attribute name Sep 30 20:22:18 jay postfix/qmgr[10510]: warning: private/smtp socket: malformed response Sep 30 20:22:18 jay postfix/qmgr[10510]: qmgr_transport_throttle: transport smtp: status: 4.3.0 reason: unknown mail transport error Sep 30 20:22:18 jay postfix/qmgr[10510]: warning: transport smtp failure -- see a previous warning/fatal/panic logfile record for the problem description The output from postconf -n: alias_database = hash:/etc/aliases alias_maps = hash:/etc/aliases bounce_queue_lifetime = 3d command_directory = /usr/sbin config_directory = /etc/postfix daemon_directory = /usr/libexec/postfix debug_peer_level = 2 fast_flush_domains = drexel.edu, cabrini.edu, medaille.edu html_directory = no in_flow_delay = 0 inet_interfaces = all local_recipient_maps = $alias_maps mail_owner = postfix mailq_path = /usr/bin/mailq.postfix manpage_directory = /usr/share/man maximal_queue_lifetime = 3d mydestination = localhost myhostname = lists.drexel.edu mynetworks = 127.0.0.0/8 newaliases_path = /usr/bin/newaliases.postfix queue_directory = /var/spool/postfix readme_directory = /usr/share/doc/postfix-2.3.3/README_FILES relay_domains = $mynetworks, $mydestination, lists.irttest.drexel.edu, lists.drexel.edu relay_recipient_maps = hash:/etc/postfix/aliases, ldap:ldappresence-lists, ldap:ldappresence-drexeltestlists sample_directory = /usr/share/doc/postfix-2.3.3/samples sendmail_path = /usr/sbin/sendmail.postfix setgid_group = postdrop smtpd_client_restrictions = cidr:/etc/postfix/client_access transport_maps = hash:/etc/postfix/transport, ldap:ldaproute-drexel, ldap:ldaproute-cabrini, ldap:ldaproute-drexel.com unknown_local_recipient_reject_code = 550 Please let me know if there's any more output that would be useful in debugging this. Thanks, Rich
