[MlMt] How does the Select Duplicates feature work?

[Justin Mallone]

Hi all,

I am trying to clean up a bunch of dupe emails.

I was forwarding emails from an old email account (gmail) to a new 
account (FastMail) for a while. Now I'm trying to clean up my inboxes. 
Looks like I may have around 50k duped emails.

I want to select the duplicate emails from the old email account and 
delete those, while leaving them in the new account.

I used Edit/Select Duplicates. I did a spot check and MailMate *seemed* 
to be selecting the "right" emails (from the old account) but it's too 
many emails to check manually, so I was wondering how the feature worked 
(like what criteria it used to determine which of the duplicate emails 
to select) so that I could delete with confidence :)

Thanks.

-JM