Okay so I've been having an issue off and on with e-mails from my forum; I personally am not receiving e-mails for topics I'm subscribed to, or for new private messages, which is annoying as I mostly rely on these rather than visiting the forum frequently (I mostly deal with technical issues).
However, some users have almost the opposite problem; they're receiving multiple e-mails for every update, or even receiving the same update over and over again.
I'm at a total loss as to what's causing the issue, as I've tried changing my e-mail settings (I've used both the default sendmail method, and also tried with a specific SMTP server), I've cleared out caches etc. but all to no avail it seems.
It doesn't seem like an e-mail server issue as my e-mail accounts are provided by the same host, and I've noticed no issues, it's only e-mail being sent by my forum that's encountering the problem(s) as far as I can tell.
Is there anything else I can try? I don't really know much about the internals of phpBB's e-mail messaging, it looks like it has some kind of queue that it runs periodically until all pending messages are sent, but beyond that I'm not sure what could be happening, as the queue always looks empty, even when I know some poor user is still receiving messages. I'm going to ask my hosting provider's support staff as well, but so far this seems phpBB specific.