Getting the error message "while sending end of data -- message may be sent more than once" in mail log (/var/log/maillog) mostly for those mails which are sent to a distribution list (group of people) and all such mails are stuck in mail queue. Also tomcat stopped automatically whenever mail server try to deliver such mails.

#var/log/maillog:

Oct 31 05:23:35 mail postfix/lmtp[11394]: EFA8BF2157A: to=<xyz@mydomain.com>, relay=mail.mydomain.com[192.168.xxx.xxx], delay=20, status=deferred (lost connection with mail.mydomain.com[192.168.xxx.xxx] while sending end of data -- message may be sent more than once)

[zimbra@mail ~]$ zmcontrol v
Release 4.5.9_GA_1454.RHEL4_20071016192012 RHEL4 FOSS edition

[zimbra@mail ~]$ zmlocalconfig |grep mem
mysql_memory_percent = 30
tomcat_java_heap_memory_percent = 50
[zimbra@mail ~]$

[zimbra@mail ~]$ zmperditionctl status
imap4 is not running
imap4s is not running
pop3 is not running
pop3s is not running
[zimbra@mail ~]$