[Biker_GA]

While forcing a user to change would be a welcome addition, a mod of this type would need to go further in order to be truly useful for an Administrator.

1. Some users may not log in for months, sometimes years.
2. A way needs to be found to check existing email addresses and verify if they're still valid. (HELO comes to mind for this.)
3. After the tool is run, any invalid email address should be flagged for Administrative action. Whether it's removing the offending email, disabling email on the account, or something else, a way should be incorporated to keep track of the invalid email addresses so action can be taken, and then give the Administrator the option of acting (delete, disable email, etc.).

I suspect email is going become a huge issue as time goes on, especially with the proliferation of blacklists, and the ease of which your site can end up on one.