How to correctly install PHPMailer + Messaging on Drupal 6
I have chosen to not use the messaging_phpmailer module and only rely on the PHPMailer module. It works now, but notification/messaging is a mess on Drupal (at least with the beta-versions I'm running). Users email addresses are copied from table users to table notifications(.destination) and table messaging_destination(.address), and sometimes it is not. Maybe it happened during update, but I had to manually update the two via SQL updates, before notification works,. Until I did, the log was filling up with PHPMailer errors 'Invalid Address'.
What's worse, when a user changes his e-mail, the subscriptions copies are not updated, so notifications are still send to the first email address.
You have to tell your users to unsubscribe before changing email, and then subscribe again...

Kind regards
The Roadrunner