outlook 2016 on Mac - "Mailbox already exists" error.

I'm surely sorry to hear that IMAP Idle wasn't a resolution to your issues, and trying Apple's Mail app might be a useful alternative (even if not ideal).

I've hung in there with MS Office 365 including Outlook for now, though my "Mailbox already exists" errors went away when I down-sized my InBox. I haven't seen the problem for many months, though experience tells me that Outlook - even when run on a Windows environment - has "quirks" when the Mailbox files becomes (for Microsoft) oversized.

My reasoning for trying to make Outlook work - beyond liking the categories and views it provides across multiple devices (Mac, iPad and iPhone) has been it's better ability to handle meeting invites. I have found it better at that task than Mail on my Mac, or BusyCal. And since I keep the family's itinerary via my calendar, it remains a critical feature for me.

A downside has definitely been receiving invites from others (e.g., Gmail .ics invites or 3rd party subscribed calendars) which automatically associate with Apple's Calendar app, not Outlook. I have never found a way aroudn this, beyond having the sender re-do the invite to my outlook.com address (whichI don't advertise or use for emailing).

I'll be very interested to hear how your conversion to Apple's Mail and Calendar apps works out for you. For now, it also represents my fall-back position, for that time in the future when the "Mailbox already exists" issue resurfaces for me.

Doug

No problem.  Unfortunately my update is that even after switching to IMAP Idle, and Outlook for Mac working well for about 2 hours this morning, the same error still reared it's ugly head:

Mailbox Already Exists

Even before it crashed, I'm not sure it was working well enough.  Seems like it was taking too long for folders to update or for me to be notified of new unread messages in folders.  

After the 4th time in 4 days during a busy work day, I've officially given up on Outlook for Mac.  Typical Microsoft quality I guess.  I bought a Mac to get away from Microsoft, and now I remember why.  

I'm on to Mac Mail.  I don't like how Mac Mail separates your Inbox, and I don't like that there are no keyboard commands for moving messages (in Outlook you CMD + SHIFT + M then type your folder name and press Enter).

But Mac Mail is superior in many other ways.

• easier scheduling in iCal
• easier addition of contacts stores in iCloud
• view attachments in-line in body of email without having to click or open them
• clearer organization of replies and forwards on email thread
• faster, smoother, more reliable, has never crashed
• emails send and receive/appear very quickly
• drag and drop to move emails to folders is faster and smoother than Outlook

So while it doesn't "look" as pretty, it at least works.  So I'm making due.  It's not worth spending any more time deleting and adding my accounts in Outlook just to keep getting this stupid "Mailbox Already Exists" error which cripples the entire email client.

Len - thanks for sharing this detailed reply on "IMAP Idle" chock full of specific info. It's great food for thought.

Happy to report that after the most recent Office 365 update my outlook problems with my IMAP Comcast accounts seems to have gone away!  So happy. If you have not yet done so, install this latest update immediately!!!

As I mentioned in my previous email, a suggestion to extend time to 15minutes on sync... after 1 week, the problem has not resurfaced.

SOLVED!

Well as the post above me agrees and I must say myself I set the time to 10 minutes and the problem seems to be less frequent. I haven't noticed it happening since, but I didn't pay close close attention to truly keep track. I'll write back but must say it has seemed to help.