Q: Yosemite: Duplicate Sent E-mails in Apple Mail

This (to my knowledge) only happens with Mail App and MS Outlook/Live/Hotmail accounts. I suspect Apple and MS know about this but neither one is in a hurry to fix it as it is part of their passive aggressive relationship.

Anyway, the problem is that both Outlook.com and Mail app save a copy of the email message in the Outlook.com server (in Sent folder) . One needs to stop doing it and that's Apple because the Server should always have primacy. (in case the Outlook user switches to other clients).

Mail App (Version 8.0 (1990.1)) in Yosemite DOES have an option to do that (See image below) but unchecking that empties the Sent folder altogether and you no longer have access to your Sent messages located in the server and you can only see the ones sent after you made this change.

Maybe someone knows a workaround but this is simply ridiculous. MS Outlook 2011 client for Mac handles these things flawlessly.

Update:

After unchecking the "Store sent messages on the server" option, the Mail app does two things:

1- It continues to save one copy locally to your computer and those are the messages you see in your Sent folder.

2- It creates another folder called "Sent" located below your folders on the left pane. This one contains the sent emails saved in the Outlook.com server.

A clumsy and cluttered solution IMO.

Send Apple feedback. They won't answer, but at least will know there is a problem. If enough people send feedback, it may get the problem solved sooner.

Mail/Provide Mail Feedback

Try rebuilding the mailbox. This can take awhile if you have a lot of mail.

Rebuild mailbox

If that doesn't work, try re-indexing the mailboxes. This can take awhile if you have a lot of mail.

Reindex messages      Mavericks/Yosemite

I am having this issue as well with my new Mac. I spoke to an Apple sr. rep and he states everything is set up perfectly on the Apple side. He referred me to Microsoft who, of course, states there's nothing they can do. They are aware of the issue and recommend using Outlook instead of Mail.

Any other ideas???

Sets the outgoing SMTP mail server to "none."

I solved it!

UUpdate - after hours trying to fix this on my own, I had a senior support specialist at Apple solve the issue. I had to reload the mail library in a specific manner...and that fixed the problems. 

In a new problem, all mail sent from my Mail program via the Hotmail server creates duplicate sent mail items. Hotmail says this is an Apple issue and apple says it's a Hotmail issue.

Great.

I'm having this problem or a similar version of it. I use gmail for my primary email address. I am seeing multiple emails in my sent folder that look like they are a snapshot of the email I am writing taken at various times as I am working on the email. If I walk away from something I am writing I may find 50 or more of these saved "drafts" in the sent folder. I have also found emails I decided not to send (after I calmed down) in the sent folder - This is really frightening if you decided not to send a particularly offensive email and then see it in the sent folder. I had 1,536 emails in my sent folder over the last month. There should have been maybe 300.

Had the same problem after I changed my iPhone. It is an iCloud issue.

On your iPhone > setting >iCloud, disable mail.

On Mac >mail >preferences >accounts >iCloud >uncheck  "enable this account".

This worked for me, no double emails. Plus i don't need my mail to be saved on iCloud, if its already saving everything on its own. hope that helps.

Solved.