I think there was a similar discussion but I cannot find it :-[
I just send a newsletter and I have some bounced email addresses. What should I do with these users? Is there a way to set the account as inactive and at first login ask the user to change his email address? (this is how xf works)
At the moment there isn't.
In 1.1 code there is already some handling of bounces, though it works (AFAIU) when using SMTP emails (for technical reasons).
There is still some (quite a bit of) work to do on that part, though.
The bounce detection in 1.1 is limited for sure, just the beginnings of "something", but its a ways off.
Part of this I guess will be to add them to a specific group, or bounced group, that gives them limited permissions to post, view boards, etc, but can update their profile with a new email address. You really don't want to do that automatically though, lots of legit reasons for bounces as well, its not always the users issue.