Message Notification Service not working

[landyvlad]

So here's an odd one. And worse, it appears to be affecting some users but not all.

One of my admins said to me:

I had a member pm me this evening who has been trying to contact (via a pm on the forum) another member since last Wednesday. Whilst I correctly got notification of his message when I logged onto the forum this evening, in the past I have always received an email notifying me that a message is "waiting" for me - I didn't get this (and thinking on it, I used to get email notifications of new members joining - but I no longer get those either.

Have you turned off the email notification service?

Obviously I hadn't so I asked him more questions and he responded.

I haven't changed my profile, also in having checked it, everything is set correctly. It all used to work, but for some time now I've not received ANY email messages, be they from PM's or notifications of new members joining.

I suspect others experiencing this issue haven't changed anything either.

Browser cache etc you mention I clear down regularly, virtually every day.

I agree that there shouldn't be any difference, but why it works for some and not others I have no idea.

SO I know of one admin for whom it is working fine (locate in NZ) one for whom it isn't (located in UK) and various members in UK for who it isn't working.

I'm at a loss/

Does anyone have suggestions as to how I might diagnose and fix this please?

SMF 2.0.19
Haven't made any changes recently at all - not to PHP or database or mods or permissions or anything.

[savo]

I had this problem earlier this year. 

The website/forum I maintain has an executive group and anytime an email is sent via the Contact Us form, it auto-forwards to all the executives and whoever is best suited to answer will reply.  We were hit with lots of spammers and alot of them were sending porn related spam.  After some poking around, I found these type of error messages in the system email accessed via cPanel. 

host cm.websitewelcome.com [100.42.49.18]
    SMTP error from remote mail server after end of data:
    552 5.2.0 User ** administratively prohibited:
    user has sent a high volume of mail detected as spam in last 24 hours

Some email domains accepted it such as my personal email but people with Gmail or Hotmail, would be blocked.

I contacted Bluehost to see if they could do anything and they fixed up the TXT record and my mail record was pointing to the wrong IP address.  They fixed them both up but emails were still not going through however I was no longer getting the 552 5.2.0 bounce back anymore.

I eventually ended up going into the Mail settings (Admin, Maintenance, Mail) of the forum and changing the Mail type from PHP to SMTP and added the SMTP settings and now we are getting emails again.  I've also added a whole bunch of email filters in cPanel to stop the spam from going out and it has helped also. 

[landyvlad]

Thanks Savo I will look into that.

Because - and this is likely the cause - I just remembered that I moved to another host (I did about 10 websites at once so it didn't ring a bell in my mind about this issue).

Thanks heaps!

[a10]

Maybe of interest (regarding php mail)

https://www.simplemachines.org/community/index.php?topic=583541.msg4134651#msg4134651