First, I must say I am new here and I love Zimbra for such a wonderful product.
Okay, back to my problem. Well, I have ZCS 6.0.10 running on CentOS 5 for more than a year without issues. Then only thing that happens once in a blue moon is that some users often are not able to receive emails from one another. That means, userA@example.com sents to userB@example.com, userC@example.com and userD@example.com, they don't get it. The clue is that this email had some attachments. If the user were to resend a test email without any attachments, they get it.
I have scourged through the /var/log/zimbra.log but could not find what is causing the issue. I see 'Passed CLEAN', '250 2.0.0 OK' and 'queued_as:' which tells me that all is okay.
Is there something I may have missed out?