How to fix Outlook 2016 for Mac crashes and doesn’t send e-mail

by | Mar 7, 2015 | Post, Technology and Innovation | 60 comments

This week’s announcement that a preview of the new Office 2016 for Mac is now officially available was a little surprise to me. I knew it was coming, but didn’t expect it to be available already. Ok, it is “just” a preview and may be you shouldn’t use it for your business, but on the other hand why not give it a try. Recent previews of Microsoft solutions are rather stable. So, I tried, but the installation included some unpleasant surprises.

1. Hard to download

Office 2011 for Mac used to be a lot better than the version for the Windows users several years ago. The launch of Office 2013 meant a huge upgrade for the Windows user. One of the biggest advantages of Office 2013 is the integration with among others SharePoint and OneDrive. Working with SharePoint has been a rather painful job on a Mac. Office 2016 will improve everything for the Mac users and therefore many of them seemed to request for the free download since Microsoft announced its availability on their blog.

Microsoft’s servers were rather slow or not responding. They were clearly not prepared for such a high demand.

2. Yosemite is needed

In case you did not yet upgrade your OS X to Yosemite, this will be the first thing to do. I kept postponing this, because I was too afraid it would influence my Windows 8 Bootcamp setup.

After securing my most essential files I decided just to do it.

The upgrade went smooth. In case you need support in upgrading you will find the instructions here.

3. Outlook crashed at startup

Once I had the Office 2016 installation file available the process went rather smooth at first. Only the Outlook setup took long. I decided not to import my Outlook 2011 settings, because I hardly used it anymore. I decided to connect Outlook to my companies Office 365 account.

And then it crashed ….. Rebooting, reinstalling, etc. just didn’t help. It didn’t want to run anymore.

Thanks to all those great online support forums I managed to find the solution. Previous settings that Outlook left behind had to be deleted with the following simple steps:

  1. Open Terminal (click the Spotlight search glass in the top right corner and type terminal)
  2. Type: defaults delete (to delete the old preferences)
  3. Type: killall cfprefsd (to kill the cached prefs)
  4. Launch Outlook

4. Outlook keeps asking for activation

May be connecting to my Office 365 account was not to be the best idea. Outlook kept requesting for activation. Online I didn’t manage to find a satisfactory solution.

I decided to uninstall again, but this time Outlook only. By the end of last year Outlook for Mac already has been released and you can download it from Office 365 and that’s what I did. I don’t know whether this is a different version, but it didn’t ask for activation.

Just to be sure I performed the above described preferences cleaning process as well.

My mail and calendar data started synchronizing!

5. Mail not sending

Full of regained enthusiasm, the whole process started with downloading efforts a day earlier, I prepared the first  messages. Quite important ones.

Murphy stayed with me. Mails were not leaving my outbox. At first I even thought they were gone, but fortunately the backup plan worked. Yes, I agree I should have send a text message first. The green dots next to the accounts on the account settings page had convinced me everything worked fine.

Outlook showed the error:

Unexpected data was encountered – error code 17997

Trying several online mentioned solutions didn’t help me much. The mail remained in the outbox. Most probably I was facing an identity issue. 

I decided to create my account once again, without deleting the initial one. I was concerned that removing my account might remove the draft messages as well. This meant I duplicated my account. 

And magically this account immediately sent the first test message. Curiously I opened one of my still pending e-mails and assigned the new mailbox as the sender address. Yes, all sent. Then I just removed the initially installed account. 

6. It’s rather slow

After all these installation issues I could have given up, but I still wanted to experience the new office. 

When you are used to Office 2013 you will find some similarities, but it feels very different as well due to the fact it has been adjusted to OSX and especially Yosemite. Personally I prefer the Office 2013 interface. The clear file menu of 2013 is really missing. For example to share a document you will have to find the sharing icon in the top right corner. In my case at first Word didn’t manage to send a file as attachment. After a reboot it started working, but preparing the e-mail took long.

And that is a general issue I have been facing while testing. The Office applications respond slow. 

May be this is due to synchronization of mailboxes and indexing, the future will tell. 

The good news is that Office 2016 is a big step forward. Integration with external storage works like a charm and that can cause I will return from my Windows 8 Bootcamp to Yosemite with Office 2016!


  1. torgerson

    Fantastic.. the preference solution fixed my issue. Thanks!

  2. IJsbrand van Rijn

    Thanks, this helped me as well!

  3. Peter Berge

    Thank you. I had the same problem with Outlook 2016 crashing and the fix worked perfectly.

      • Yael

        the fix did not work for me 🙁

  4. avery ng

    when i upgraded to yosemite beta the other time, outlook 2011 had this issue which it can be launched but without showing any window, i just noticed that this same thing happened to my outlook 2016, i just updated its latest update though, the startup crash thing (no. 3) i encountered before and it has been resolved with that fix, may i know what can i do with this problem 🙁

  5. Russell Smith

    Helpful article for handling error code 17997. I hope, all bugs will be fixed by Microsoft as soon possible.

  6. Jason Richards

    Thank you for the crash fix. It has been a big help.

  7. Jason

    You think YOU have a problem sending emails? I recently discovered a HUGE problem – Some of my Outlook for Mac 2016 imap accounts randomly won’t connect for any foreseeable reason. (While others stay connected. Restarting outlook fixes the this).

    The BIG problem occurs is when I don’t notice an account is “not connected” and I SEND an email, I hear the sending tone as if it did sent, but the email VANISHES. Nowhere. Nada. Not in drafts. Not in outbox (like it should be). Not on the server. Restarting outlook doesn’t resurrect the email and send it. It’s GONE as far as I can tell.

    So now EVERY EMAIL I SEND I have to copy, paste to be safe. Then send. Then check my sent items to ensure it REALLY went out. How awful.

    I contacted Microsoft and they said we need to just get used to vanishing emails now that Hillary taught us it’s acceptable, but they will pay $50,000 to the first person on a forum who can fix my problem or recover my vanished emails since they can’t. Anyone game to help?? Thanks in advance…

    • PetersOpinion

      Jason, thanks for your reply. I haven’t faced the issue to the extend as you described it, but I’ve noticed that e-mails are disappearing. Till now I thought I just didn’t remember whether or not I had send them. Reading your comment it might be that I sent them, but Outlook didn’t. I’m facing connection issues as well. I’m connecting to Office 365 and frequently this connection seems to be hanging or it takes Outlook really long to get connected. Unfortunately, till now I didn’t find a satisfying solution for that.

      Let’s hope Microsoft (or someone else) will get this fixed soon.

  8. Steve Douglas

    Recently installed Office 2016 on a new Macbook Air.. migrated from a PC. I have to say it is generally very impressive apart from a few bugs here and there. The major problem though is the email issue noted below, i.e. that of emails going missing. It is odd that emails seem to be sent, but they are not actually sent. This urgently needs to be fixed as the program cannot be used not knowing if vital emails go or not. What seems incredible is that there is very poor means of providing feedback to the office development team. You would have thought they want as much information as possible to improve the product. Why is it big companies seem to loose the basic concept of connecting with customers?

  9. The SMS

    Hi Guys, I tried the delete & kill in terminal and when I restarted outlook it goes through the first few steps of start up and then just hangs and doesn’t finish opening up. Any other suggestions?

  10. Rich

    Hi all, jsut had the exact same ‘disappearing email’ thing happen. I spent about an hour writing a very complex, in depth email, and very proud with my work, I sent it. I got the whooooshing ‘send’ noise from my mac and was happy that a VERY important mail ahd gone.

    I went to my sent folder to see that it definitely had been sent before closing my Mac down, and it wasn’t there. I went to my drafts… not there. No outbox was showing up…. I checked my internet connection, all good. Then I notice that Outlook for Mac 15 was saying ‘sync pending for the folder’ on the account I had sent the mail from. So I reconnected to the internet, tried hitting ‘send and receive’ and eventually the message changed to ‘All folders are up to date’. Phew – the mail must have gone now…. Nope. Not in sent folder, not in drafts, not in outbox, not in trash. It’s as if the mail never existed and I never sent it. I’m gutted… I’ll have to write it out all over again and send from a browser mail email client as I can no longer trust Outlook for Mac…. Grrrrrr!!!!

  11. Nick Flynn

    Hi … I have a recently occurring issue with Outlook 2016 … loaded onto iMac and Macbook about a month ago, and all worked fine until last week. One one account, and just on the iMac, I keep getting error -3253 … Connection to the server failed or was dropped. Mail on the iMac works fine, and I have no problems with iPhone and iPad. Outlook on my Macbook Pro works OK too.

    The weird thing is that having left the iMac switched off over the weekend. I did get some mail coming down first thing on Monday morning, but as soon as I tried to Send/Receive, I got the same error message.

    I did check, and the problem seems to be with incoming mail, as I have received mail send out from the account in question on the iMac using Mail.

    Do you have any suggestions??? Many thanks

    • Abdul Ahad

      I m also facing the same issue. Did you get fix to your problem?

      • Nick Flynn

        To be honest Abdul … The problem resolved, I just assumed that it was fixed by an update … sorry I couldn’t be more helpful

  12. Jakeyk

    If you have Office 2011 installed make sure that you run updates through 2011 before opening Outlook 2016. The Error reporter needs to update to 2.2.9 or it will crash Outlook 2016.

  13. Peter Francis

    Many thanks for the resolution. I tried a number of times to install Outlook 2016 & got the hideous error message. Tried your fix & all working now! Thanks!!

  14. Carmen Soto

    i having problems with this new office on my mac ios 10.10.4. its super slow and word never opens, keeps crashing and asking me if i want to send the report. sometimes i send it, sometimes i just ignore it because its not solving anything. i work with this tool, so this problems are definitely interrupting my work. excel and outlook keeps crashing too.

    i need help!

    • PetersOpinion

      Hi Carmen, sorry to hear that. For me it’s running ok for regular documents. Bigger Powerpoint and Word files are more challenging. In the beginning I noticed the new Office was a bit slow, probably due to indexing, but after a day it got for sure better. What other applications are you using at the same time? Are you having a browser opened with many active tabs may be? Especially when it’s Google Chrome it’s going to be a challenge. When office apps keep crashing even after a reboot, I would consider reinstalling (I agree it shouldn’t be like that, but it once worked for me as well).

    • Tom G

      I got the same problem. And none of the solutions I’ve found seem to have worked out. What to do….? Apparently, the start-up procedure for any of the Office apps blocks somewhere only a few seconds after having logged in on the company’s Office 365 account…

      What I have tried already:
      -deleting caches (seemed to work at first but then again it kept on crashing a bit later on in the process
      -reinstalling Office: didn’t help
      -following the above tip with commands in terminal

      Please help because I can’t work with my essential Office apps for over a week now..


  15. Leonard Stewart

    I am curious if anyone else is having an issue with their mouse. I am running OSX10.10.4 and Microsoft Outlook for Mac 15.11.2, and since installing, I notice that my mouse pointer and what it selects on the screen do not line up. That is to say that while I point at one name/mail item/column, it actually highlights/selects the one above.

    Although generally present, the problem does seem to come and goes – and the amount of difference/disparity changes by minimizing and opening up the window again! I can not find a real pattern as to when it comes or goes, although sometimes by opening and closing the ribbon bar I can fix the issue altogether, and other times it just changes the disparity a bit.

    Anyone seeing this issue also?

    • Lianne Ames

      I’ve run into this problem. Usually after Outlook has crashed. Try changing your reading pane view. If you have it at the bottom, change to side, or vice versa, then back. It should clear up. I couldn’t quite figure it out either the first time it happened.

  16. kabby82

    canyou please tell me what the fix is. My outlook 2016 hangs and crashes and also results in giving me disk space issues on the mac.

  17. erict

    The latest version only syncs at startup and then doesnt receive any new mail. Has anyone else seen this? Any fixes?

  18. Jim Rives

    after MUCH time with Apple and GoDaddy, found that Outlook in Office 2016 for MAC reduces my 20 mps service to about 10 mps – all the time! When I close Outlook – it pops immediately back to 20 mps. Now using Apple Mail and internet speed is back to max. A tech at GoDaddy told me this is a problem with Outlook 2016 – especially if you have much in the inbox. My inbox is empty and still reduces speed.

  19. S Mid

    I am having issues when I c&p from a word document. The formatting gets all jacked up. I can c&p from any other source with no issues. What happens is that the sentences shorten and go to the next line, so I have to backspace, delete, etc., to get it to look proper. Probably a simple fix, but I need help!

  20. maria

    When i try to install it it asks me my e-mail, is that normal?

  21. Dennis Connelly

    All mac 2016 applications freeze if I try to print. Any suggestions?

    • inverse137

      Yes. uninstall and go back to Office 2011 for Mac.

  22. guysesnet

    My exchange account on outlook 2016 won’t send mail and often disconnects. The wierd thing is that having outlook 2016 open also prevents apple mail from sending mail out. Do they interfere with each other?

  23. Stephane Durande

    Hi, I do the following :

    Open Terminal (click the Spotlight search glass in the top right corner and type terminal)
    Type: defaults delete (to delete the old preferences)
    Type: killall cfprefsd (to kill the cached prefs)
    Launch Outlook
    And ??? i’ve got nothing … i lost all my archive’s …

  24. Ludovic Leforestier

    Still doesn’t offer feature parity with the Windows version and has incompatibilities with SharePoint when two+ users are simultaneously editing a document on the server.

    The other issue I have is that the Sync with My Day is gone (it doesn’t see the online calendar anymore).

  25. Joshua Kord Nelson

    AHH! Worked so beautifully! 🙂 Thanks! 🙂

    • PetersOpinion

      Nice to know the post keeps making people happy. Thanks for sharing.

  26. Andrew Brindley

    My Outlook 2016 still crashes. I used the beta version initially that crashed so I went back to 2011 for a while. Then I couldn’t open sharepoint docs in office 2011 so as a 365 user advised to move to office 2016. Did this again found outlook just crashes again. Used the advice for terminal above but made no difference. So Im using the new office 2016 apps and 2011 for outlook which is a pain. I have also tried to install it twice but this made no difference.

    • PetersOpinion

      Hmmm, that’s a pity. Once I faced a similar issue. After removing Outlook, I decided to reboot before installing it again and then it worked. Did you try that? It that doesn’t help it will be hard to support you remotely without having any details.

  27. Eric Y. Theriault

    In case it helps others, I was experiencing a similar issue where when I
    started Outlook, it would just become “unresponsive”. I tried all of
    the recipes online to no avail. The way I fixed my machine was to exit
    out of Excel and OneNote, and then it would startup just fine. Not sure
    what that was about, but I’m back up and running. Thanks.

    • PetersOpinion

      Thanks for sharing this tip. It seems to work for others as well!

  28. Michael Carter

    I have just installed Office 2016 and all went well except when I try to send an email, Outlook crashes. Every time. Whether replying or with a newly composed email. Any suggestions?

  29. inverse137

    Outlook 2016 for mac doesn’t work very well. I have problems on both the macs I have it installed on. Better off waiting for patches/updates or keeping OUtlook 2011

    • PetersOpinion

      What OS X do you have installed? Have you upgraded to OS X El Capitan already? Outlook seems (still) not to work well on El Capitan. For me that was a sufficient reason to wait with upgrading until there is a patch available. On Yosemite I am not having any issues with Outlook 2016.

  30. inverse137

    office 2016 for mac really isn’t very good.

  31. Sue

    I keep getting an error code -3253. How can I fix this?

  32. Nikita

    I have two email accounts linked to Outlook 2016 but I keep getting this error message when I try and email from one of my email accounts.

  33. Carlos Jearmy

    Outlook Customer Care 18557771707 Toll Free Helpline.(Usa Canada)

  34. FC68

    For the error -3253 with messages “Connecting securely to smpt….” or Connection to the server failed or was dropped the only solution after hours of work was to get new port number for STMP server from email provider and SSL needed to be turned on. NOTHING worked that I had on Thunderbird or Mac Mail flawlessly. On outlook special port required… NOT fun.

  35. Peter Gregory

    I have a Yosemite version 10.10.5 and outlook 15.24. The issue here is that I am typing a message an without warning or should i say box drops down for a microsecond so you can’t see what it says. then it suddenly stops letting me type.
    I have to position the cursor at the point where it stopped to continue.

    Any advice please pm**@am***.au

  36. Jerry

    I’m using an older (6 or 7 yrs old?) mac mini with software version 10.5.8, and last month Outlook updated itself. Now I can’t see any of the contents of the various folders (Inbox, Sent, Drafts – etc etc). This Mac Mini won’t accommodate any further software upgrades, per Apple and local mac shops.

    Is there any way to deal with the Outlook limitation rather than dealing with the limitation of the older mac mini?

    Thanks in advance!!


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