Hi All
When i go to bed Zimbra is okey, but when i wake up and try checking my Email i will see POP3 and SMTP Servers are dead!

here is my zimbra.log around FATAL ERROR

Code:
Dec 20 04:46:14 234 zimbramon[15797]: 15797:info: 2006-12-20 04:46:03, STATUS: localhost: antispam: Running
Dec 20 04:46:14 234 zimbramon[15797]: 15797:info: 2006-12-20 04:46:03, STATUS: localhost: antivirus: Stopped
Dec 20 04:46:14 234 zimbramon[15797]: 15797:info: 2006-12-20 04:46:03, STATUS: localhost: ldap: Running
Dec 20 04:46:14 234 zimbramon[15797]: 15797:info: 2006-12-20 04:46:03, STATUS: localhost: logger: Running
Dec 20 04:46:14 234 zimbramon[15797]: 15797:info: 2006-12-20 04:46:03, STATUS: localhost: mailbox: Running
Dec 20 04:46:14 234 zimbramon[15797]: 15797:info: 2006-12-20 04:46:03, STATUS: localhost: mta: Running
Dec 20 04:46:14 234 zimbramon[15797]: 15797:info: 2006-12-20 04:46:03, STATUS: localhost: snmp: Running
Dec 20 04:46:37 234 postfix/smtpd[16210]: connect from domain.com[72.232.248.26]
Dec 20 04:46:38 234 postfix/smtpd[16210]: NOQUEUE: reject: RCPT from domain.com[72.232.248.26]: 550 <domain@domain.com>: Recipient$
Dec 20 04:46:38 234 postfix/smtpd[16210]: lost connection after RCPT from domain.com[72.232.248.26]
Dec 20 04:46:38 234 postfix/smtpd[16210]: disconnect from domain.com[72.232.248.26]
Dec 20 04:46:46 234 amavis[23223]: Net::Server: 2006/12/20-04:46:46 Server closing!
Dec 20 04:46:51 234 postfix/postfix-script: stopping the Postfix mail system
Dec 20 04:46:51 234 postfix/master[22921]: terminating on signal 15
Dec 20 04:46:52 234 zmtomcatmgr[16449]: threaddump requested
Dec 20 04:46:52 234 zmtomcatmgr[22631]: sending SIQUIT to tomcat/JVM process 22632
Dec 20 04:46:54 234 zmtomcatmgr[16459]: stop requested
Dec 20 04:46:54 234 zmtomcatmgr[16459]: waiting for manager process 22631 to die
Dec 20 04:46:54 234 zmtomcatmgr[22631]: shutdown requested, sending TERM signal to 22632
Dec 20 04:46:58 234 zmtomcatmgr[22631]: tomcat/JVM process exited (waitpid expected 22632 got 22632)
Dec 20 04:46:58 234 zmtomcatmgr[22631]: manager woke up from wait on tomcat/JVM with pid 22632
Dec 20 04:46:59 234 zmtomcatmgr[16459]: manager process 22631 died, shutdown completed
Dec 20 04:48:11 234 zmtomcatmgr[16954]: status requested
Dec 20 04:48:11 234 zmtomcatmgr[16954]: file /opt/zimbra/log/zmtomcatmgr.pid does not exist
Dec 20 04:48:11 234 zmtomcatmgr[16954]: assuming no other instance is running
Dec 20 04:48:11 234 zmtomcatmgr[16954]: no manager process is running
Dec 20 04:48:13 234 amavis[16907]: starting.  /opt/zimbra/amavisd/sbin/amavisd at localhost amavisd-new-2.4.1 (20060508), Unicode aware$
Dec 20 04:48:13 234 amavis[16907]: user=502, EUID: 502 (502);  group=, EGID: 502 502 89 5 (502 502 89 5); log_level=1
Dec 20 04:48:13 234 amavis[16907]: Perl version               5.008008
Dec 20 10:48:13 234 postfix/postqueue[16964]: fatal: Queue report unavailable - mail system is down
Dec 20 04:48:14 234 zimbramon[16683]: 16683:info: 2006-12-20 04:48:01, STATUS: localhost: antispam: Stopped
Dec 20 04:48:14 234 zimbramon[16683]: 16683:info: 2006-12-20 04:48:01, STATUS: localhost: antivirus: Stopped
Dec 20 04:48:14 234 zimbramon[16683]: 16683:info: 2006-12-20 04:48:01, STATUS: localhost: ldap: Running
Dec 20 04:48:14 234 zimbramon[16683]: 16683:info: 2006-12-20 04:48:01, STATUS: localhost: logger: Running
Dec 20 04:48:14 234 zimbramon[16683]: 16683:info: 2006-12-20 04:48:01, STATUS: localhost: mailbox: Stopped
Dec 20 04:48:14 234 zimbramon[16683]: 16683:info: 2006-12-20 04:48:01, STATUS: localhost: mta: Stopped
Dec 20 04:48:14 234 zimbramon[16683]: 16683:info: 2006-12-20 04:48:01, STATUS: localhost: snmp: Running
here is my memory usage
Code:
# free -m
             total       used       free     shared    buffers     cached
Mem:          1962       1628        333          0         36        972
-/+ buffers/cache:        618       1343
Swap:         1992          0       1992
where is my problem ?
how can i fix?