duplicate email notifications

I’ve been receiving duplicate email notifications, for comments. For example, I have a saved comment notification that was made on 2.25.2005 for a legitimate, approved message (while the WP software was running on v.1.2.2) I received a duplicate email message of that one from 2.25 today, sent from the WP system on 5.3.2005.

I have received other duplicate email notifications, but didn’t really think much of them, and simply deleted them from my inbox, so I can’t go back and make solid inferences about the duplicates’ periodicity. Now, since I realize there’s a problem of some kind, I’ll be saving them routinely and hopefully note whether they are correlated with post edits or other apparent activity such as spam, etc.

Has anyone else had this problem? Any idea what’s happening? Any solutions?

I’ll likely bump this thread if I have additional information to add.

I made some test comments. These were from me logged in as me..
1. On a post with other comments existing results in no emailing of previous duplicates, only the current message.
2. On a post with no other comments results in no emailing of previous duplicates.

How about a test trackback? I can’t test trackbacks received on this blog since upgrading to 1.5. But I receive trackback spams.

Hypothesis: Duplicate emails of comments previously approved are being sent with new occurrences of apparent trackback spam that’s been moderated.