I hate to say the obvious, but without further information, it would appear that the user failed to follow the menu links:
Username > Account Settings > Edit Personal Information > Change Email
and did something else.
I had understood that the user would receive copies of deleted posts, so it should have been possible for them to re-post their messages - although the links to replies would become broken. However, I just tried deleting a message in my test forum, and I have yet to receive a copy of the deleted post.
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.