Hello, I have a production server, which worked fine until stop sending and receiving messages today.
zimbra@mail selinux]$ zmcontrol -v
Release 6.0.10_GA_2692.RHEL5_64_20101215170845 CentOS5_64 FOSS edition.

[zimbra@mail root]$ zmcontrol status
Host mail.dominio.com.br
antispam Running
antivirus Running
ldap Running
logger Running
mailbox Running
mta Stopped
postfix is not running
snmp Running
spell Running
stats Running
[zimbra@mail root]$
The logs: /var/log/zimbra.log:
Aug 15 09:22:02 mail postfix/postfix-script[15669]: fatal: Postfix integrity check failed!
Aug 15 09:22:25 mail postfix/postfix-script[17444]: fatal: the Postfix mail system is not running
Aug 15 09:23:30 mail postfix/postfix-script[18165]: warning: not owned by postfix: /opt/zimbra/data/postfix/./spool/pid/inet.465
Aug 15 09:23:30 mail postfix/postfix-script[18166]: warning: not owned by postfix: /opt/zimbra/data/postfix/./spool/pid/unix.trace
Aug 15 09:23:30 mail postfix/postfix-script[18167]: warning: not owned by postfix: /opt/zimbra/data/postfix/./spool/pid/inet.submission
Aug 15 09:23:30 mail postfix/postfix-script[18168]: warning: not owned by postfix: /opt/zimbra/data/postfix/./spool/pid/unix.retry
Aug 15 09:23:30 mail postfix/postfix-script[18169]: warning: not owned by postfix: /opt/zimbra/data/postfix/./spool/pid/unix.error
Aug 15 12:30:13 mail postfix/postqueue[12518]: fatal: Queue report unavailable - mail system is down
Aug 15 12:40:02 mail postfix/postqueue[26209]: fatal: Queue report unavailable - mail system is down
Aug 15 09:47:01 mail postfix/postfix-script[6309]: fatal: Postfix integrity check failed!

The permissions on the folders:
/opt/zimbra/data/postfix
[root@mail selinux]# ll /opt/zimbra/data/postfix/
total 12
-rw------- 1 postfix postfix 33 Jul 19 16:02 master.lock
-rw------- 1 postfix postfix 1024 Ago 15 08:29 prng_exch
drwxr-xr-x 16 postfix postfix 4096 Jan 6 2011 spool
[root@mail selinux]#
/zimbra/data
[root@mail selinux]# ll /opt/zimbra/data/
total 28
drwxr-xr-x 2 zimbra zimbra 4096 Jan 6 2011 altermime
drwxr-xr-x 7 zimbra zimbra 4096 Ago 15 09:29 amavisd
drwxr-xr-x 3 zimbra zimbra 4096 Jan 6 2011 clamav
drwxr-xr-x 2 zimbra zimbra 4096 Jan 6 2011 dspam
drwxr-xr-x 4 zimbra zimbra 4096 Jan 14 2011 ldap
drwxr-xr-x 3 postfix zimbra 4096 Jan 6 2011 postfix
drwxr-xr-x 9 zimbra zimbra 4096 Ago 15 10:02 tmp
[root@mail selinux]#

I saw several threads here in the forum, but still could not solve the problem. Thank you.