Don't know if this still happens under 1.2.1 but at least under 1.0.3, the following misbehavior happens. We had a user account with a non-existing email address. When Confluence sends the change notifications to the account, the sending obviously fails during the SMTP handshake. Now, our administrator just noticed Confluence had tried to send a change notification email 11458 times during the last 24 hours - just to this one account. Some other accounts are also similarly getting resends of the change emails.

Since there's no way to tell the problem exists other than noticing an email server is slowing down, I'd prefer someone check the logic for retrying to send a change notification.