>> I installed iRedmail-0.6.0 Based on CentOS 5.5. Mail send/receive everything was OK.
>> But from yesterday, I faced problem of receiving e-mail.
>>  I checked maillog, dovecot.log,messages, mysql.log but no solution observed. What can I do now?

please check the maillog herewith:

Mar 21 04:02:36 host2 postfix/pickup[4742]: 67C3E7D011C: uid=0 from=<root>
Mar 21 04:02:36 host2 postfix/cleanup[5136]: 67C3E7D011C: message-id=<20110320220236.67C3E7D011C@host2.batworld.com>
Mar 21 04:02:36 host2 postfix/qmgr[2227]: 67C3E7D011C: from=<root@host2.batworld.com>, size=899, nrcpt=1 (queue active)
Mar 21 04:02:36 host2 postfix/trivial-rewrite[5282]: warning: do not list domain host2.batworld.com in BOTH mydestination and virtual_mailbox_domains
Mar 21 04:02:36 host2 postfix/pipe[5142]: 67C3E7D011C: to=<root@host2.batworld.com>, relay=dovecot, delay=4.7, delays=4.7/0/0/0, dsn=5.3.0, status=bounced (Command died with signal 11: "/usr/libexec/dovecot/deliver")
Mar 21 04:02:36 host2 postfix/cleanup[5136]: 71FDD7D0120: message-id=<20110320220236.71FDD7D0120@host2.batworld.com>
Mar 21 04:02:36 host2 postfix/bounce[5144]: 67C3E7D011C: sender non-delivery notification: 71FDD7D0120
Mar 21 04:02:36 host2 postfix/qmgr[2227]: 67C3E7D011C: removed
Mar 21 04:02:36 host2 postfix/qmgr[2227]: 71FDD7D0120: from=<>, size=2674, nrcpt=1 (queue active)
Mar 21 04:02:36 host2 postfix/trivial-rewrite[5282]: warning: do not list domain host2.batworld.com in BOTH mydestination and virtual_mailbox_domains
Mar 21 04:02:36 host2 postfix/pipe[5142]: 71FDD7D0120: to=<root@host2.batworld.com>, relay=dovecot, delay=0.02, delays=0.01/0/0/0, dsn=5.3.0, status=bounced (Command died with signal 11: "/usr/libexec/dovecot/deliver")
Mar 21 04:02:36 host2 postfix/qmgr[2227]: 71FDD7D0120: removed
Mar 21 06:01:01 host2 policyd-cleanup: clean up process starting: policyd v1.82
Mar 21 06:01:01 host2 policyd-cleanup: connecting to mysql database: 127.0.0.1
Mar 21 06:01:01 host2 policyd-cleanup: connected..
Mar 21 06:01:01 host2 policyd-cleanup: expiring throttlesender records older than 31 days (1297987261)
Mar 21 06:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 06:01:01 host2 policyd-cleanup: expiring throttlesender instances older than 1 hour (1300662061)
Mar 21 06:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 06:01:01 host2 policyd-cleanup: clean up process starting: policyd v1.82
Mar 21 06:01:01 host2 policyd-cleanup: connecting to mysql database: 127.0.0.1
Mar 21 06:01:01 host2 policyd-cleanup: connected..
Mar 21 06:01:01 host2 policyd-cleanup: expiring validated records older than 7 days (1300060861)
Mar 21 06:01:01 host2 policyd-cleanup: expired: 1 records
Mar 21 06:01:01 host2 policyd-cleanup: expiring unvalidated records older than 2 days (1300492861)
Mar 21 06:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 06:01:01 host2 policyd-cleanup: expiring blacklisted records (1300665661)
Mar 21 06:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 06:01:01 host2 policyd-cleanup: expiring autowhitelisted records older than 7 days (1300665661)
Mar 21 06:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 06:01:01 host2 policyd-cleanup: expiring helo records older than 7 days (1300665661)
Mar 21 06:01:01 host2 policyd-cleanup: expired: 5 records
Mar 21 06:01:01 host2 policyd-cleanup: expiring throttlerecipient records older than 31 days (1297987261)
Mar 21 06:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 08:01:01 host2 policyd-cleanup: clean up process starting: policyd v1.82
Mar 21 08:01:01 host2 policyd-cleanup: connecting to mysql database: 127.0.0.1
Mar 21 08:01:01 host2 policyd-cleanup: connected..
Mar 21 08:01:01 host2 policyd-cleanup: expiring validated records older than 7 days (1300068061)
Mar 21 08:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 08:01:01 host2 policyd-cleanup: expiring unvalidated records older than 2 days (1300500061)
Mar 21 08:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 08:01:01 host2 policyd-cleanup: expiring blacklisted records (1300672861)
Mar 21 08:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 08:01:01 host2 policyd-cleanup: expiring autowhitelisted records older than 7 days (1300672861)
Mar 21 08:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 08:01:01 host2 policyd-cleanup: expiring helo records older than 7 days (1300672861)
Mar 21 08:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 08:01:01 host2 policyd-cleanup: expiring throttlerecipient records older than 31 days (1297994461)
Mar 21 08:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 08:01:01 host2 policyd-cleanup: clean up process starting: policyd v1.82
Mar 21 08:01:01 host2 policyd-cleanup: connecting to mysql database: 127.0.0.1
Mar 21 08:01:01 host2 policyd-cleanup: connected..
Mar 21 08:01:01 host2 policyd-cleanup: expiring throttlesender records older than 31 days (1297994461)
Mar 21 08:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 08:01:01 host2 policyd-cleanup: expiring throttlesender instances older than 1 hour (1300669261)
Mar 21 08:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 10:01:01 host2 policyd-cleanup: clean up process starting: policyd v1.82
Mar 21 10:01:01 host2 policyd-cleanup: connecting to mysql database: 127.0.0.1
Mar 21 10:01:01 host2 policyd-cleanup: connected..
Mar 21 10:01:01 host2 policyd-cleanup: expiring validated records older than 7 days (1300075261)
Mar 21 10:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 10:01:01 host2 policyd-cleanup: expiring unvalidated records older than 2 days (1300507261)
Mar 21 10:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 10:01:01 host2 policyd-cleanup: expiring blacklisted records (1300680061)
Mar 21 10:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 10:01:01 host2 policyd-cleanup: expiring autowhitelisted records older than 7 days (1300680061)
Mar 21 10:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 10:01:01 host2 policyd-cleanup: expiring helo records older than 7 days (1300680061)
Mar 21 10:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 10:01:01 host2 policyd-cleanup: expiring throttlerecipient records older than 31 days (1298001661)
Mar 21 10:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 10:01:01 host2 policyd-cleanup: clean up process starting: policyd v1.82
Mar 21 10:01:01 host2 policyd-cleanup: connecting to mysql database: 127.0.0.1
Mar 21 10:01:01 host2 policyd-cleanup: connected..
Mar 21 10:01:01 host2 policyd-cleanup: expiring throttlesender records older than 31 days (1298001661)
Mar 21 10:01:01 host2 policyd-cleanup: expired: 0 records
Mar 21 10:01:01 host2 policyd-cleanup: expiring throttlesender instances older than 1 hour (1300676461)
Mar 21 10:01:01 host2 policyd-cleanup: expired: 0 records