Outlook Insider not starting

Copper Contributor

My Outlook, since upgrading to the latest Insider build (Version 2206 Build 16.0.15321.20000) 64-bit , stop starting, just sitting on the splash screen stating it was "opening profile".  I have created a new profile and while my old MSN e-mail will load, as soon as I add an Office 365 account, it stops working. After multiple start / stops, it will get to my MSN inbox, but then I'm faced with a white screen of death.


It is as if it can no longer work with O365 accounts.  I have several and I have tried more than one.


I've tried starting with outlook /safe, but while it may start, I still move to the white screen of death when I click on items.


Should I wait long enough, I can see my mail boxes, but if I try to expand an Office 365 mailbox by clicking on the ">" in the folder list, I get this appear, eventually:



Any suggestions?  I'm running Windows 11, Dev Insider too.  I've got 100gb free in disk space, 64GB ram etc, so I do not think I have a resources issue.

9 Replies
Same here, upgraded to insider version 2206 Build 16.0.15321.20000, 365 no longer works. I have to reinstall current version to get it working again.

@David Overton It's a bug in this "Experiments" section, some of which have been known to cause problems before and which you can delete. Note that it comes back upon restarting Outlook the first or second time, so you'll need to do this again until it's fixed in an upcoming build. You may see one or two things go away when doing this, like the "Coming Soon" toggle as well as the new-style left-side navigator, but who cares.





16.0.15330.20004 is now out, but it takes a while for "Experiments" to return so I don't know if it's fixed or not. Someone who never deleted Experiments would know.


Update: Looks like the problem is still there. Upon further testing, at least here it relates specifically to 1.28 here:




I would suggest just deleting 1.28, if you have it.

@David Overton @xyzxyzxyz With a workaround as a stopgap (see above), I'm starting to wonder why I see this problem with some and not others when everyone is using an Exchange account.


Do you have any ideas? Could the version of Windows be involved? What are you running? It does happen that the one having the issue is on Win11 Dev (25xxx) while the one who doesn't is on Win11 22H2 (22621), but I find it hard to believe that's it.


It might also be something about the Exchange account, as there are countless variables there, but we've tried multiple ones (in different profiles) and that so far hasn't been the answer. It remains consistent one way or the other: always a problem or never one.

@Brian . It is definitely more complex.


I created another user on my system and could not repro the issues once I joined all the accounts.  This suggests it is a profile specific issue as the other user had access to the same accounts, but e-mail worked fine.


What I can say is that I've done a clean install of the latest Windows 11 Dev build and the issue has gone away.  I can say I was able to stop the problem for a while by removing accounts from "Settings / Accounts / E-mail & Accounts", so it sounds linked, but in the end, a clean install solved my problem. Same OS, same Exchange, same accounts, same Office - different result.

@David Overton 

Yes, by coincidence I was going to try another Windows profile today (and still will). Sounds like that will work, which does make some sense given the evidence, but it's hard to connect that with the Registry hack that I mentioned, which is extremely Office specific. I can't even imagine what it could be about Windows suddenly that Office is objecting to, but it must be something.


(Previously, I had tried doing the other thing you mentioned: removing the registered account in Windows Settings, as a logical step before creating a new Outlook profile, but that wasn't the answer.)


It sounds like the problem started for you with a Dev build upgrade. That's something that I was never sure about here, since I did a Dev build upgrade and 15321 in very close proximity to each other. I've yet to find any mention of the issue in Feedback Hub, and you would think that someone would have mentioned it there even if it's not really a Windows problem but more a Windows ricochet.


I won't be doing a Windows clean install, that's for sure (you're more ambitious than I).

I Guess this is conflicts due to POP3 and IMAP email data compatibility and supporting.
@Dhetechup - are you sure you posted this to the right thread? There has been no mention of POP3 or IMAP and in my case, all of my accounts are Outlook or Office 365 accounts and are HTTP connections, not POP3 or IMAP.

.ost is an offline storage table (orphaned file of Server email database) that requires authentication so one can open and read emails. ESP connection and server connectivity