dovecot.lda-dupes

What is the purpose and/or use of the dovecot.lda-dupes file that (sometimes) exists in the home folder for each user?

I've seen some posts about issues with the file or losing track of the location, etc, but nothing on what the file actually does or how it could be useful. I assume it is just a dovecot file that helps not keep track of … I guess duplicate mails?

It looks like it contains the message-ids and email destinations for certain, but not all, duplicate emails, but in a binary format.

-- "The good news: Hadron Collider went live and did not destroy ALL reality. Bad: I'm the only one who remembers President Gore's 2 terms." --Andy Ihnatko