Cannot Verify Server Identity. The identity of @outlook.office365.com@ cannot be verified.

Hi Cheyenne_99

Good day to you.

From your description, you first can change the network environment to check the result. As far as I know, the unstable network would lead to the verifying failure. Besides, you can also try to disable SSL feature to check if it is workable (Access to Settings> Password&Account> Select the exchange account> Advance>turn off SSL on iPad). Furthermore, you can re-start iPad to check if it works.

If the issue persists, to provide further assistance, we’d like to know what you use mail app, such as Outlook, Mail, etc. In addition, does the issue appears when you sign your account in other devices?

Looking forward to your update.

Regards,

Joey

Thanks @Joey Dong MSFT

That's helpful.  I could try using the Outlook app instead of relying on Apple's iOS Mail, Calendar and Contacts apps, but would prefer have all my various email, calendars and contact accounts in one app, rather than splitting them across two different apps, which could cut down speed of working.  I will try turning the iPad off (again), then also try turning off SSL and see if that makes a difference, will this compromise security though?  

I use Outlook on Windows 10, an iPhone and a Surface laptop, none of those are reporting this error.  My previous iPhone 7 was prone to this error, but my current iPhone X and iPhone 11 do not have this problem.  Perhaps this would indicate some incompatibility between older iOS devices and current Exchange Server settings.  The iPad is three years old.

URGENT!  I have the same problem "the identity of outlook.office365.com cannot be identified" - but my problem is not on iPhone or ipad but on my PC laptop. I use Outlook365 on Microsoft exchange server. It stopped working yesterday with the above message. I am not able to work without my Outlook working!  HELP!

I am having the same issue.  A co-worker of mine is getting that message on their iPhone.  On a Laptop, I used Edge to navigate to outlook.office365.com and the page will not load.  The Security icon for the site (looks like a padlock when secure in the box to the left of the url address textbox) keeps on alternating between the globe icon and this padlock.  The page will not load eventually.  I tried the same thing with outlook.office.com.  When I cancel the load after a few minutes, I get a page can not be loaded message on the browser with the following details:

cId: 509D2AC2D92B47EF95188EEBE4863DD2

app: Mail

st: 401

reqid: null

wsver: null

efe: DM5PR07CA0161, BL0PR02CA0059

ebe: DM6PR02MB4826

et: ServerError

esrc: UserBootSettings

err: Error: 401

estack: Error: 401

   at Anonymous function (https://outlook.office.com/mail/login.html:343:33204)

   at Anonymous function (https://outlook.office.com/mail/login.html:350:29828)

   at r (https://outlook.office.com/mail/login.html:350:32981)

ts: 2020-07-28 11:24:09Z

I see this on iPhone and iPad, both running MSFT's own Outlook app, not the browser.  Both on my home internet (>100Mbps) and at the office (>50Mbps fiber).

Notice the other commenter here is seeing it on Windows.

One might conclude this problem is not explained by the OS, browser or connectivity.  It's a software problem.  I realize intermittently exhibiting software bugs are very hard to fix, but that's what this appears to be.