email reply creates duplicate draft after sending when using gmail accounts

issue is likely with gmail not outlook. you'll see the same complain with mac, em, iphone users

Dear Michael Futterman

Thanks for using Microsoft products and posting in the Community.

If there is no problem with exchange mailboxes but all Gmail mailboxes have problems, it means that there is no problem with new outlook for mac, just a compatibility problem with Gmail mailboxes.

You feedback that you are not using classic outlook, so you can't switch over because you don't have a license for classic outlook.

I'm not sure if you are using add-ons? You can click on Tools - Add-ons to see if you have add-ons, if so, you can try uninstalling or disabling them.

I'm on a test machine, outlook version is also 16.91.1 (24111613), configured with a Gmail test mailbox, and sending emails, or replying to other people's emails, no duplicate drafts appear.

So my suggestion is whether you can reinstall outlook once again, and then instead of configuring an exchange protocol mailbox first, configure a Gmail mailbox first, and check if you will have this problem. Also, Gmail mailboxes can't create rules on the new outlook for mac again, so about the way mark for deletion will automatically delete, can you turn it off first. Overall it's re Gmail web side, you adjust some settings to default first. Then you can configure Gmail mailbox to outlook to determine whether the adjusted settings are causing the outlook conflict.

Best wishes

Clark | Microsoft Community Support Specialist

Both boxes.

I deleted the one that I use more and it is currently creating a bigger problem for me in that all the sent emails that I use to reference my follow ups do not seem to be in the sent folder. Not great.

I've never used classic and only used the current version with this email address.

I keep Outlook and all my Microsoft Apps up to date and this has been occurring through multiple updates over the last year.

Dear Michael Futterman

Thanks for using Microsoft products and posting in the Community.

For what you describe, I would like to confirm a question, do you have this problem with both your Gmail mailboxes? Are the other mailboxes having this issue?

If the other mailboxes don't have this problem, but only one of the Gmail mailboxes has this problem, you can delete the Gmail mailbox and reconfigure the Gmail mailbox to check if it is normal.

If both Gmail mailboxes have the problem and other mailboxes don't have this problem, this may be caused by the compatibility problem of Gmail mailboxes.

Is this problem occurring after you updated to the new outlook using classic outlook? That is to say classic outlook works fine, but the new outlook has this problem? If yes, you can switch to classic outlook and continue using it.

You can click on outlook at the top, click on classic outlook and check the box that says switch to classic outlook.

Also, has your new outlook been updated recently or is this problem recent, if so it could be a compatibility issue with Gmail after the new outlook has been updated. You can try to rollback to the previous version.

Update history for Office for Mac - Office release notes | Microsoft Learn 

Looking forward to your reply.

Best wishes

Clark | Microsoft Community Support Specialist