Out of the box, XenForo shouldn't have any issues sending mail, as we use the default PHP configuration. If you have changed either board to use SMTP to send mail (via the email options), then that is a likely culprit. I would check the settings and possibly move back to the default method.
However, if you haven't changed the boards from the default, then this likely indicates a misconfiguration in PHP or a mail server/MTA that isn't running properly. The only way to really check the MTA level is to look at the mail logs and confirm that the emails are actually being sent. (This would require root access to the server. If you don't have that, you'll need to contact your host to let them know that mail isn't being sent.)
I have the default setting checked, but mine isn't working either. My host uses an IMAP server, and has the usual mail.domain_name.com port 143 configuration. Is that not the "default" setting? And if I need a password to send an email via Thunderbird, why wouldn't I have it on XenForo? Sorry if I am being thick, it's just that I am thick at times!
I should also note that it will send "test emails", just not real ones.......
Admin CP -> Home -> Options -> Email Options -> Email Transport Method
"Default" means your forum is using the mail settings in the PHP configuration. If emails aren't working then that means PHP's mail settings are wrong or the mail server is having problems (contact your host).
Alternatively, if you have a specific SMTP server you want to use for outgoing emails then you can select "SMTP" and enter the credentials for the server.
I'm not getting a test email either
I just switched over from vb and we used the normal "email users" it in with no problems, so I wouldn't think it would be a PHP issue but I do wonder what you guys are talking about when you say it might be the PHP?
(nvm, I figured out what I broke, it's working fine now)
nope - nor me - running "standard" new install (1.0.3) on new server. No mails. just checked 1.0.3 on my previous server - no emails on that either.... Cant see that two different servers from two different suppliers would have this incorrect (tho i guess it is possible!)
If your site is getting a massive amount of traffic to deal with, it might just be the postfix queue or sendmail queue is full. Go through the host, or a control panel interface to this queue to inspect. Once done, either flush it, or restart the mail daemon.
From SSH, try running "sendmail -q", this could clear the mailqueue by attempting to send the mails, and upon failure deleting them from the queue. Otherwise, contact your host to see what's up. (Which I see Paul did, so that's great!)
Did you import users from another system into XenForo?
Today I noticed that I wasn't receiving emails and I was scratching my head because everything else worked on my server regarding email. Then, I decided to update my email address and suddenly email worked fine! Maybe there's something with the import process that is preventing mail to be sent from XenForo until the user updates it. I'm looking into it.