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I'm having an issue that's related to 115 as I didn't have this problem on 102. This is also not related to gmail, live.com, icloud or other exchange accounts, only my IMAP accounts are having this problem. I have it set to a unified folder and I display both sent and inbox in the thread. Some of the items in the inbox show twice and some, if not most of the items in the sent folder on the thread show twice as well.

Don't know what else I could say more than what's in subject. Tried deleting all emails in inbox can't do it. Thunderbird freezes up. There's 45,000 emails in inbox suddenly. Have combed and read comments seems no help anywhere. Anybody please help.