Yes, the test message was titled, "Test 22". Yes, the content on both duplicates in TB 115 was identical so if I delete one, the other disappears too. The account is [email protected] I highlighted it to the left. You can see in the pic that the email on top was to [email protected] (my real estate address), which is having the same problem BTW as it's also with infomaniak (the emails that I am having duplicate on TB are only occuring with this provider). But as you can see, inside webmail of infomaniak that there is the original message, to [email protected], and the return message (sent message) from [email protected]. No duplicates occur here, but inside of TB 115, the return message is duplicated. The "Bryan Me 2" is just saying how many message are in that thread, 2 messages.

So far, all the images show what is in the 'Unified Inbox' and only in one particular mail account.

Do you see the duplicates in the mail account 'Inbox' folder? Do you see the duplicates in the mail account 'Sent' folder?

Yes, sometimes I see duplicates in both the inbox and sent box. Only in unified view and only in TB 115. This didn't happen with the same profile in 102. This doesn't happen in Postbox which is based on TB102, nor in EMClient, Outlook, Mac Mail, MailMate, etc... This problem only occurs in 115. Is there any way I can get 102 back? I'm not impressed.

https://bugzilla.mozilla.org/show_bug.cgi?id=1849770 is similar. https://bugzilla.mozilla.org/show_bug.cgi?id=1844007 is also collecting some information.

Thank you for looking into it. I'm glad it's being worked on.