Rated 5 out of 5 stars

I just installed this add-on and it does exactly what I wanted. Thank you.

I have two questions. Firstly, what does the menu entry with the very long name actually do? The only difference I can see is that the next time (ond only that one time) I select "Remove Duplicates ..." I see a pop-up saying "not checking special folders".

And secondly, why are so many comparison options needed? Isn't it sufficient to just compare on comparing the message-id and date headers? (That is what my other mail client does, and I have always found it sufficient.)

This review is for a previous version of the add-on (0.3.12). 

1. It means that in your next dupe search, only dupes of messages found in the folder(s) you marked as "originals folders" will come up.

For example, suppose you have folders F1 with messages m1, m2 and folder F2 with messages m4, m5, m6. Assume that m1=m4 and m5=m6. If you don't set originals folders, and search for dupes in F1 and F2 together, you'll get two dupe sets: { {m1,m4}, {m5,m6} } ; but if F1 is the "originals folder", you'll only get { {m1,m4} } .

2. Different people want to use different comparison criteria. Your suggestion is sufficient for your use case... if someone sent you the same message, once via a mailing list and a second time directly, the message ID will probably be different, and the date also (well, date received anyway). So - you would need other criteria for this scenario.

Thanks for the positive review.