I have a phpBB Server, currently 3.0.6, but this issue has existed previously, that is sending out email notifications to users about updates to threads that have been deleted. The user can click on the link in the email and it will just take them to a page saying the thread does not exist.
Sometimes it sends out 20+ such emails to the same users a day, this is not affecting all threads or users, just a few, and only on specific threads. I have tried looking in the SQL database for references to this thread to see where it is maintaining the thread watch list or some other place where it is linking this deleted thread to the affected users, but have had no success.
I found a file called queue.php and a file called queue.php.lock in the cache folder which were not deleted when the cache was purged using ACP. These files appeared to hold information related to the mass email. I deleted them manually which should, for now, stop the repeated sending of emails.
By default, phpBB will only send one notification email to each user subscribed to the topic when someone replies. Additional replies will not send more notifications UNTIL the user visits the topic again.
1) User subscribes to a topic
2) Someone replies to the topic and a notification email is sent out
4) Someone else replies to the topic, no notification email is sent
5) User visits the topic again
6) Someone replies to the topic, so another single email is sent out.
The reasoning for this is simple: Say you subscribe to a topic. Then say 100 people reply to the topic before you've had a chance to read it again. Every single user subscribed to the topic would receive 100 emails, which puts quite a strain on both the server as well as spamming your email inbox.
The SMTP settings in the ACP should be the same settings you use inside of Outlook. The server is typically your domain name. This isn't always the case, but it will be the same as the "Outgoing" mail settings in Outlook. The username and password is the same that you use in Outlook.