Has this been fixed

I’m using the free version… thinking of buying the paid version, but am concerned… has the deduplication function been fixed.  I just ran it against a folder with 246 emails… at least 1/2 of them are duplicate subject lines… the response was “no duplicates found”… I won’t upgrade or recommend this product to my clients and friends if the newer version doesn’t fix this

It works just fine, so maybe there is some misunderstanding of exactly what it does.

The Deduplicator does not look for the same subject lines, because when you reply or forward a message, the subject line may be the same but the messages certainly aren’t. Instead it looks for duplicate messages that may be in your database because you copied a message to multiple folders, or even received the same message on multiple email accounts. 

Each and every message sent through the Internet has a unique message ID. That means no two message will ever have the same ID. Even when they are replies or forwards of an original message, each one has a unique ID something like <5e9afc689cef6_561772132071b@ip-10-36-…>.   eM Client’s Deduplicator looks for these.

But if it is not working for you when it should be, here is something you can check. If you have two messages that you think are duplicates, right-click on the header section in the message preview pane (the area where the from and to addresses are) and choose View Mail Header. Then scroll down to find the Message-ID. Make a note of it and then do the same with the suspected duplicate. If the IDs are not the same, they are not duplicates.

I too am using the trial version but wish to buy the pro with all future upgrades but am receiving 3 emails with exactly the same identification code per email. please fix it or I will migrate elsewhere.

Is this happening with all messages?

Do you have the same email account setup more than once in eM Client?