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Outlook 2016 Authentication/Autodiscover issue introduced in October 2018 RRS feed

  • Question

  • Hi there,

    One user (me--I was the lucky winner), recently started receiving authentication prompts in Outlook 2016. We run exchange 2010 SP3 in-house. We have a single domain with two sites, roaming profiles. Anyhow, I received the authentication prompts, and it would not accept a known good password. I tried tracing back my steps, and feel the authentication prompt started after deleting my cached user profile copy on the local machine. The prompts would also occur on any machine that I had never signed into (and therefore lacked a cached profile copy).

    Tried deleting and rebuilding the mail profile and that did not resolve. Ultimately, I found some other admins on the internet had a similar issue in January 2018, and the work-around offered at the time was to enter a registry key (DWORD ExcludeExplicitO365Endpoint=1) under HKCU\Software\Microsoft\Office\16.0\Outlook\Autodiscover . This reg entry stopped the prompts for me.

    However, I was concerned, because:

    1. The info that came with the reg entry said it was specific to a bug introduced to Outlook in January 2018 but the bug has since been fixed and MS even kind of said "don't use this registry entry to fix this any more."
    2. Also, this reg entry would indicate the cause of the authentication prompt was that Outlook was trying to authenticate to O365... but we are an in-house exchange shop... why would Outlook try to reach out to O365 when there is an on-prem exchange server?
    3. Last, the reg entry only fixes it on the specific computer to which it is applied. I continued to receive the login prompts on other endpoints.


    I suspected it was a bug in a recent Office build. I rolled back from build 10827.20150 to build 10827.20138 but that did not resolve. I then rolled back Office one more step to build 10730.20102 and that seemed to do the trick. I could now open Outlook on a machine without a local profile and without the registry entry.

    Anyone else run into this this month, or are we the unlucky ones? Seems like a bug, and hopefully one that will be fixed in a future Office update.

    • Moved by Steve Fan Tuesday, October 16, 2018 8:38 AM relocate
    Monday, October 15, 2018 4:00 PM

All replies

  • Dear Matthew,

    authenticating still works well. 

    With the update autodiscover seems to stopped working a in an hybrid setup I get error about querying the free/busy times. 

    I tried to setup an account yesterday an autodiscover didn't work. I had to populate the servers myself. 

    Tried testing autodiscover with Exchange Connectivity-Tool I can not perform the test as the captcha is not recognized and I didn't make a typo.

    So there are some issues... Hope this helps. You are not alone

    Bernhard

    Tuesday, October 16, 2018 7:05 AM
  • Hi Matthew,

    >>Also, this reg entry would indicate the cause of the authentication prompt was that Outlook was trying to authenticate to O365... but we are an in-house exchange shop... why would Outlook try to reach out to O365 when there is an on-prem exchange server?

    Based on my research, with the current channel Click-to-Run release of Outlook 2016, Outlook uses a set of heuristics to determine whether the user account provided comes from Office 365. It doesn't matter whether you are using an Office 365 account or not, it's just one of the steps in the AutoDiscover process. If this step does not retrieve a payload, Outlook moves to next step in the process. It looks something caused Outlook to stuck in this step and not automatically move to next step.

    >>I suspected it was a bug in a recent Office build. I rolled back from build 10827.20150 to build 10827.20138 but that did not resolve. I then rolled back Office one more step to build 10730.20102 and that seemed to do the trick.

    We haven't received any report on this issue recently in the forum. I'll keep monitoring on this issue and keep you updated once I get some more info.

    Regards,
    Steve Fan


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    • Proposed as answer by Steve Fan Friday, October 19, 2018 9:12 AM
    Tuesday, October 16, 2018 8:38 AM
  • Just wanted to say hi and check if there is anything that I can do for you on this problem. If so, please do not hesitate to let me know and I will be happy to help.

    Best regards,
    Steve Fan 


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.


    Click here to learn more. Visit the dedicated forum to share, explore and talk to experts about Microsoft Teams.

    Friday, October 19, 2018 9:13 AM