We're experiencing a problem where we seem to have pretty random periods of postfix timing out when trying to deliver a message. This is causing lots of deferrals and delayed messages for our users. The hardest part in figuring this out is that it seems pretty random.
I can send 10 messages to my gmail account which arrive immediately but then I send another and it's delayed for a few hours. Here's an example from our latest mail stats.
954 deferred (5804 deferrals)
The Zimbra support team is telling us to check firewall settings. They all seem fine and if the firewall was blocking a specific port, wouldn't it be causing more of a problem, not this seemingly random one?
Has anyone experienced anything similar to this? Any thoughts?