PERSISTENT PROBLEM: Duplicated emails in Mail (Outlook) Sent folder

Thank you, tbirdvet.

Sounds good and makes sense and I did of course look for a solution that would remove Sents from the server, except I cannot mirror your instructions on my system. Apologies if I wasn't clear. I'm on a MacBook Air 2022 Ventura. Outlook is a 3rd party app as part of my Microsoft 365 package, not a stand-alone executable, and looking at Outlook/Settings/ [note, there is not "preferences"] there is no further menu to go to--it just shows my default (only) account/email address. I can go to Outlook.live.com, but there's no "advanced" anything in the Settings (preferences) there, hence no "Folders" or "Sent" section either, so I cannot simulate your perfectly reasonable suggested debug, which is rather frustrating. I am grateful for your further guidance if this clarifies my dilemma.

Yes, as I've indicated, I have contacted both Apple and Microsoft.

It appears resetting up my Outlook mail through Exchange is the solution and having done so, I was able to uncheck the box for saving Sents on the server, which option didn't exist in the IMAP Outlook account.

So, this closes out this issue I think.

Cheers and have a great day.

Yes. Please know that I did not willy-nilly come here, but carefully looked at the problem and potential fixes before posting here. I know that this is a user to user support site--I have had my account with Apple since 2006 as originally set up with my outlook address.

Since Apple sells users the Mac with the Microsoft apps designed to work on their machines, it is reasonable to expect they have some responsibility for ensuring compatibility. (I happen to have MS 365 so didn't have to purchase the programs again.) Apple allows for email clients of all descriptions to work within/through Apple's Mail program (gmail, yahoo, outlook, etc.) In fact, Apple and Microsoft have a working agreement since 1997 and Apple has a whole website devoted to accommodating Microsoft programs on their Macs. See macOS - Compatibility - Apple Apple was brilliant to open their doors to accommodate the business world.

Anyway, I'm sure you know this is not about fault-finding. It's about solution-finding to a problem both companies are having with their users whom they care about. Other users have reported the problem and it is reasonable to think that while of course I contacted Microsoft right away, someone here may have encountered the same or similar issue, as in fact they have which is referenced in my initial post. (See which: Duplicated emails in Mail (Outlook) Sent … - Apple Community)

The first solution given in this thread may have also been somewhere in Apple solutions, but those steps are not evident/available on this Mac I'm using. And actually, those are the exact steps Microsoft provides on its help pages for the problem. Evidently they were accidentally omitted somewhere along the line in updates or new versions.

As is so often the case (55%-80% of the time) a failure mode occurs at the interfaces. This is pretty clearly an interface problem because the steps to fix the trouble did previously exist in earlier versions of Macs and/or Outlook and appear to now be missing.

As you say, maybe someone in this forum, besides the one I cited, will have encountered the same issue and know of a solution. In any case, both Apple and Microsoft are now aware of it and hopefully will collaborate to restore the previous compatibility.

P.S. I think I did mention that this issue has only begun when I bought and started using my MacAir which was Mar 2nd. That's date coincident with the problem occurring. I don't know my way around the belly of Mac whereas I knew PCs and Windows like the back of my hand. It also did not happen on my iPad for the year+ that I was only using it for emails, until I started using the Mac. . . . if that helps at all.

MS Support used to be great. I have always been paid customer and could call and talk with someone. No more. Support now only on line unless they decide they must call you--which they did today, but resolved nothing. Tech Support was ESL and couldn't understand or be understood and I wasted a couple hours getting nowhere because he insisted I do something that is not in the Apple Outlook app to do and then left me hanging in silence while he was off checking with someone for periods up to 20 mins.

Anyway... Essentially, for an IMAP account there needs to be a way to tell the Apple Outlook app not to return Sent emails from the server back to the sender. At present, the Apple app has no way to enable a setting to do this, which brings it back to Apple to come up with a work-around even if Apple has to coordinate with MS to do so. The User cannot do it and MS can't tweak an Apple app. Catch 22 for the user. 🤨

And, speaking with Microsoft on the phone just now, it does seem they should be the ones to handle, but the one I spoke with was in a different team and has bumped my concern to the right team for Outlook issues.

Thanks for your attention to this. Whenever my issue gets resolved, I will update this thread.

Last answer for today after doing a lot of testing through all possible permutations of sending mail using my outlook address....

The problem ONLY occurs when I send mail using Apple Mail and only on my Mac.

It does not occur when sending mail with outlook address from Mail on my iPad.

It does not occur when I use the Outlook app (either the newer app or the legacy) separately from the Mail program on my Mac.

Nor does it occur sending from outlook.live.com on the web.

I have yet to hear back from Microsoft, but from this it definitely seems to be a problem ONLY manifesting while using Apple's Mail program.

Therefore, the solution must be between Mac and Microsoft talking to each other to fix it. From this testing it seems clear the bug is in Apple's programming for Mail.

If anyone sees a logic flaw here, I'm open to help if for no other reason than I've spent way too much time and I want to learn. Thanks!

OK. The package of programs that comprise MS Office 365 function the same as the stand-alone programs. There is just much more one can do with 365 in terms of cloud, support, and how the programs all can interact with each other.

Yes, as I've indicated, I have contacted both Apple and Microsoft.

My outlook address emails do come in to my Apple Mail on my Mac and this is set up as IMAP from what I can tell. I do not know why this was automatically set up that way when I bought and began using my devices (the iPad 15 mo ago, the Mac a month and a half ago). It was not something I manually did. Possibly it was originally set up that way when I first got an iPhone before any other devices. Perhaps resetting up my Outlook mail through Exchange is the solution.

I have said I am using [Apple] Mail to which emails (to my Outlook and other addresses) come. I could, but don't, routinely separately use the Outlook app, or the Outlook.com webmail. I have chosen to use [Apple] Mail in order to have easy access to all my email from each of my email addresses come to one place. And it is only in Apple Mail that sents are duplicated--they are not duplicated when sending mail from Outlook.com or the Outlook app on my devices as I explained. I have since been able to ascertain that there used to be a setting available to turn off keeping sents on the server, but this somewhere got dropped in some update or new version of Outlook's app.

I didn't come here to ask anyone to "make either company 'aware' of the problem" as I know what the volunteers (whom I greatly appreciate) here do; I came simply and only to enquire if anyone else here has had the trouble and how they may have solved it. Thanks for letting me know that Apple requires tens of thousands of people having the same problem for them to pay attention. LOL. Still, call me an optimist, but I have fair confidence that eventually either Apple or Microsoft, whom I pay handsomely for support, will help if an answer hasn't turned up from the lay public meanwhile, which is why I resurrected the query here and elsewhere. In the end, perhaps Exchange is to be the answer though that didn't arise as an option when Mail was originally invoked on my iPad and later Mac.

Cheers.

The whole problem seems to have returned with the recent upgrade to Sonoma 14. Incredibly frustrating and no one seems to have a suitable permanent answer and some want to point fingers. For me, the problem only occurs when sending/receiving email with Mail -- i.e. Apple Mail program