Outlook for Mac Duplicates ATT.NET Email Messages When I Try to Delete or Move (or Send) Them

[dgrrr]

(Please read through before suggesting basic fixes -- thanks!)

On a Macbook Air M2, 2022 w Sonoma 14.0, and “Microsoft Outlook for Mac v16.77.1”:

In Outlook, ONLY for email accounts ending with “@att.net”, when I DELETE or MOVE messages to another folder within Outlook, it appears TWICE in the destination, and REMAINS in the origin folder. The messages in the SENT folder are being duped too.  IE I end up with 3 copies.

For example, when I delete an inbox msg, it momentarily disappears from inbox, then appears twice in Deleted Items, then reappears in inbox. If I re-delete the inbox message, a third copy appears in Deleted items (with another still in inbox). For some reason, when I delete the inbox copy a third time, it finally leaves the inbox permanently — but I end up with FOUR identical copies in Deleted Items.

This does NOT happen with messages sent from or moved on the webmail server at att.net.

It also does NOT happen with non-ATT email accounts in Outlook (e.g. gmail in outlook is fine).

NOTE -- when I removed and re-added these ATT accounts to outlook, I was told I needed a secure key, aka app-specific password, which I created and used.

All the above happens to TWO different att.net accounts.

Also, often the ATT folders in Outlook suddenly appear empty, with the message “sync pending for this folder”, and in some cases this persists until I restart Outlook for Mac. I BELIEVE the duplications might happen during these periods of sync-hanging.

If we delete messages via webmail, the deletion syncs downstream to Outlook normally.

IN SUMMARY, it SEEMS like Outlook for Mac doesn't have permission to "remove" files from any ATT IMAP folders, so when we try to move (aka delete) a file within those folders, the Outlooks syncing hangs, and ends up COPYING the file to the destination. And does so at least twice.

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The server settings automatically chosen by Outlook for Mac are:
imap.mail.yahoo.com 993 yes ssl
smtp.mail.yahoo.com 465 yes ssl

The “Trash” folder is set to “Trash (Server)”. Changing this to “Deleted Items (Server)” didn’t help. BUT the folder name in Outlook is “Deleted Items”. It syncs with webmail “Trash”.

I have removed these accounts and re-added them to Outlook more than once.

Thanks for any ideas!

[#2 · Accepted solution]

@dgrrr  The fix was to switch from the "old/legacy Outlook for Mac" to the "New Outlook for Mac" interface. I had assumed it was a superficial difference, but apparently not. Also beware when adding a new email account to "New Outlook", as it default to syncing with Microsoft Cloud vs just adding it as regular IMAP, i.e. "sync with google" or "sync with yahoo", etc. 

NOTE -- this fix came from Outlook for Mac's built in support chat, "Contact Support". They responded right away, in person!

[#3]

The problem is New Outlook has its own issues. You cannot transfer you contacts and it constantly signs me out of my account. There has to be a better answer than switching to new Outlook. I did that for 6 weeks and have gone back because legacy Outlook is better. I have a Yahoo mail serve and am having the same problem. Duplicates resending and deleted emails being redownloaded. Is there other ideas out there.