Okay, I'll start by saying I'm not 100% sure if the board itself is at fault, but I'm receiving some weird e-mail issues so I'm hoping someone can help me debug them.
My hosting provider handles my e-mail, but I have no control over the server, so I don't have any access to any logs that I can see. I use this for all my own personal e-mail which is continuing to work with out any issues, so it doesn't seem like the e-mail server itself is broken. However I use another, separate e-mail account for my phpBB forum as its outgoing SMTP server (as my hosting provider doesn't allow PHP/Ruby etc. to use regular sendmail).
However, I'm only getting a fraction of the e-mail that my forum should be sending to me for subscribed topics, meanwhile some users are complaining about getting multiple duplicate e-mails.
There shouldn't be an issue with the outgoing e-mail account as it deletes all incoming messages (i.e - it's only for sending e-mail), but I'm doing what I can to investigate that as a possibility as well, though as I say I don't have any logs for the e-mail server so I may have to wait for support staff to take a look.
Anyway, I'm just hoping for some suggestions about how I might debug this; is it possible this is a phpBB problem, or should I be looking somewhere else?
I just noticed that there are some E-Mail Error entries in phpBB's error log, however these don't contain any information, just the word "Backtrace" in big letters, no actual link or such (same if I look at the corresponding entry in the database), is there a way to get more information? The error message in the log is "Could not get mail server response codes".