Many users has bad email: account deleted, user suspended, no space in mailbox etc. Your mails to this users back to you with errors. This is advanced version of (SL) Force users to change email Features:
Make users unapproved until they did not change their email address
To users with bad emails did not send any emails
Approving emails by users
Move users to selected group
Log all actions
All you need for work is bad emails list. How to get users list with bad emails? 1. Manually: see your mailer-daemon letters 2. You can use special services 2. Auto: in mail error.log I am doing like this:
You get file mail.log.badmails.list where all your bad mails listed. Just copy-paste into config. Thats all. Tested with 4.3!