[Dovecot] No duplicates on imap copy?

Hello,

when from my script I try to copy messages from one imap folder into another own (within the same imap mailbox). That works perfectly, but... If I copy the same message N times from one folder into another one, in the destination folder I see N copies of the same message, each with its own UID.

I wonder if there any way to deduplicate folder content (so in the destination folder I'll get only one copy of each message)? I'd implement something like that myself in my script but I just don't know which part of the messages should I compare - probably md5 of headers?

Thank you in advance!

Yours, Alexander Chekalin