OS X 10.6 Server - Dovecot Issue

[Ian Baker]

I've just taken over support for an OS X Server (v10.6.8) box, and am a bit new at Postfix & Dovecot.

We're having an problem where, intermittently, dovecot seems to be bouncing messages inbound for some of my existing users.

Here is the mail.log entry for a successful delivery:

  Aug 21 16:58:45 mail postfix/pipe[64094]: D68783AE0F75: to=<sblondin at eem.ca>, relay=dovecot, delay=0.08, delays=0/0.01/0/0.07, dsn=2.0.0, status=sent (delivered via dovecot service)

And here is what a bounce looks like

  Aug 22 07:29:28 mail postfix/local[93916]: error: od[getpwnam_ext]: No record for user sblondin
  Aug 22 07:29:28 mail postfix/pipe[93944]: 852C43AE7ACC: to=<sblondin at eem.ca>, relay=dovecot, delay=15, delays=0.14/0.05/0/15, dsn=5.1.1, status=bounced (user unknown)

And a bit later another succcessful delivery.

  Aug 22 07:56:37 mail postfix/pipe[95021]: 14AF73AE82F0: to=<sblondin at eem.ca>, relay=dovecot, delay=0.5, delays=0.08/0.02/0/0.4, dsn=2.0.0, status=sent (delivered via dovecot service)

No changes to this user's account were made during this time period.  I'm flummoxed.

Anythoughts as to what might be going on here, and/or how to debug this further?

Thanks in advance...

Ian

/usr/sbin/dovecotd --version
1.1.20apple0.5

sh-3.2# /usr/sbin/dovecotd -n
# 1.1.20apple0.5: /private/etc/dovecot/dovecot.conf
Warning: fd limit 256 is lower than what Dovecot can use under full load (more than 456). Either grow the limit or change login_max_processes_count and max_mail_processes settings
# OS: Darwin 10.8.0 x86_64  hfs
base_dir: /var/run/dovecot
syslog_facility: local6
protocols: managesieve imaps imap
listen(default): *
listen(imap): *
listen(managesieve): *:2000
ssl_ca_file: /etc/certificates/mail.eem.ca.98CEBC1921A5C908068A7CB64F0364C1D5DEF795.chain.pem
ssl_cert_file: /etc/certificates/mail.eem.ca.98CEBC1921A5C908068A7CB64F0364C1D5DEF795.cert.pem
ssl_key_file: /etc/certificates/mail.eem.ca.98CEBC1921A5C908068A7CB64F0364C1D5DEF795.key.pem
ssl_cipher_list: ALL:!LOW:!SSLv2:!aNULL:!ADH:!eNULL
disable_plaintext_auth: no
login_dir: /var/run/dovecot/login
login_executable(default): /usr/libexec/dovecot/imap-login
login_executable(imap): /usr/libexec/dovecot/imap-login
login_executable(managesieve): /usr/libexec/dovecot/managesieve-login
login_user: _dovecot
login_process_per_connection: no
max_mail_processes: 200
mail_max_userip_connections(default): 20
mail_max_userip_connections(imap): 20
mail_max_userip_connections(managesieve): 10
verbose_proctitle: yes
first_valid_uid: 6
first_valid_gid: 6
mail_access_groups: mail
mail_location: maildir:/var/spool/imap/dovecot/mail/%u
mail_executable(default): /usr/libexec/dovecot/imap
mail_executable(imap): /usr/libexec/dovecot/imap
mail_executable(managesieve): /usr/libexec/dovecot/managesieve
mail_process_sharing(default): full
mail_process_sharing(imap): full
mail_process_sharing(managesieve): none
mail_max_connections(default): 5
mail_max_connections(imap): 5
mail_max_connections(managesieve): 20
mail_plugins(default): quota imap_quota
mail_plugins(imap): quota imap_quota
mail_plugins(managesieve): 
mail_plugin_dir(default): /usr/lib/dovecot/imap
mail_plugin_dir(imap): /usr/lib/dovecot/imap
mail_plugin_dir(managesieve): /usr/lib/dovecot/managesieve
sieve_storage(default): 
sieve_storage(imap): 
sieve_storage(managesieve): /var/spool/imap/dovecot/sieve-scripts/%u
sieve(default): 
sieve(imap): 
sieve(managesieve): /var/spool/imap/dovecot/sieve-scripts/%u/dovecot.sieve
lda:
 postmaster_address: postmaster at example.com
 hostname: mail.eem.ca
 mail_plugins: push_notify cmusieve quota
 quota_full_tempfail: yes
 sendmail_path: /usr/sbin/sendmail
 auth_socket_path: /var/run/dovecot/auth-master
 log_path: /var/log/mailaccess.log
 info_log_path: /var/log/mailaccess.log
auth default:
 mechanisms: plain login gssapi cram-md5
 verbose: yes
 passdb:
   driver: od
 userdb:
   driver: od
   args: partition=/etc/dovecot/partition_map.conf enforce_quotas=no
 socket:
   type: listen
   master:
     path: /var/run/dovecot/auth-master
     mode: 384
     user: _dovecot
     group: mail
plugin:
 quota_warning: storage=100%% /usr/libexec/dovecot/quota-exceeded.sh
 quota: maildir:User quota
 sieve: /var/spool/imap/dovecot/sieve-scripts/%u/dovecot.sieve