It has come to my attention that an aspect of phpbb3 email notifications, that which requires you to visit the board before you receive any more notifications, causes a problem when a post is deleted. If a user is subscribed to a thread or forum and receives a notification of a new post, and if that post is deleted before he logs in to the forum, he is unable to read said post. Thus, not satisfying the conditions of the notification, he does not receive any for the next post in the subscribed board/thread. Or if he does, it is delayed. I ran a controlled test twice - with email package size set to 50 the email was delivered 15 minutes late, with package size 0 the email never arrived. It is uncertain when the user receives notifications again. For my members it has ranged from hours to days to weeks. But obviously it's not particularly great if the notification system ceases to work properly, so this would be something worth fixing.