Forum stopped sending emails

[Sir Osis of Liver]

2.0.15 forum has been working normally, no changes I'm aware of (others work on this website).  Nothing in forum or server error logs, nothing in mail queue when enabled.  testmail.php works, emails are sent and received.  Using php mail, do not currently have server access or smtp credentials.  No emails are sent - topic notifications, admin notifications, nada.

Current SMF version: SMF 2.0.15
GD version: bundled (2.1.0 compatible)
Database Server: MySQL
MySQL version: 5.6.44-cll-lve
PHP: 7.0.33
Server version: Apache

[YogiBear]

Hi Sir Osis,

I've been hovering here for a few days to see if anyone answers this but for what it's worth maybe asking your hosting company if they've made any configuration changes could be worth a shot.

[Sir Osis of Liver]

It's one of my client forums, they're on a GoDaddy dedicated server, and I don't currently have server access.  After much dicking around, they've told me they switched to an Office 365 email system, that apparently killed php mail.  Trying to get smtp credentials, but it's like pulling teeth.  Don't understand why testmail.php works, but forum doesn't send any emails.

[m4z]

Could this be similar to this topic from a few days ago? There it seemed the receiving mail servers either rejected the mails, thinking they're spam, or accepted and put them into a spam queue that is not easily or not at all visible to the user. (The other user didn't seem to have access to the server mail logs, too, so this is mainly speculation. However, changing details of the contents "fixed" the issue.)
Or is your scenario different?

[Sir Osis of Liver]

That was a problem on the receiving end, email server was running content filters that didn't like something in the email template.  Received a topic notification this a.m., no idea what's going on, probably something on server end.  There are several people involved in managing this guy's website, forum (me), and server, and it's a GoDaddy box, they often make changes without advising account owner.  Will have to check and see if other emails are now being sent.