We've been trying to figure this one out for a couple weeks now. Using XF 1.5.1 and running PostFix 2.11.0. Many emails are being sent, but some users (most notably another admin) are only receiving notifications for a few select threads and conversations.
I had our hosting company take a look at this and they tweaked postfix to improve it's performance some, but there doesn't seem to be a problem on their end. The server reports 0 messages in the queue. Any ideas?
They should be able to look at the raw error logs to see the result of the mails being queued and sent (in case there's an error). There wouldn't be anything that would vary from conversation to conversation for example -- it should be sent consistently.
Thanks, I'm more libel to think that he is somehow having the emails intercepted. We had a similar problem when we first started when our emails were being rejected as spam by gmail and aol due to someone who used to have our domain.