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

Yes it does.

just reenable SSL after a minute or so.  Here is what i followed.

I was having the same issue on my Apple OS. The message would display every 5-10 seconds and was more than obnoxious. I went into my mail settings, i use Apple’s mail client, turned of SSL on incoming and outfoing mail servers and selected DONE. When i received the popup that log ins were disabled i hit DONE again. You will get an error message so make sure you hit DONE twice and it will force the tasks. After SSL is removed

from both incoming and outgoing servers, select DONE on the IMAP Account Informatiom screen and let it verify. If you get the error message again,

hit DONE twice to force.  It will verify credentials and complete the task. Then log back in and turn back on SSL on both servers and select done. This has corrected the issue for me.

This solution fromRobbie Hinson solved the problem for me.

I was having the same issue on my Apple OS. The message would display every 5-10 seconds and was more than obnoxious. I went into my mail settings, i use Apple’s mail client, turned of SSL on incoming and outfoing mail servers and selected DONE. When i received the popup that log ins were disabled i hit DONE again. You will get an error message so make sure you hit DONE twice and it will force the tasks. After SSL is removed

from both incoming and outgoing servers, select DONE on the IMAP Account Informatiom screen and let it verify. If you get the error message again,

hit DONE twice to force.  It will verify credentials and complete the task. Then log back in and turn back on SSL on both servers and select done. This has corrected the issue for me.

Perfect!  Problem solved.

Thank you for your wisdom!

Jeff IS THE MAN! Did the above and it worked with no issues! My main Office 365 account is nos configured and working on my iPhone. Now trying to figure out the IMAP settings for shared/alias inboxes as those are not working with the same settings.

Agreed this seems to be an IMAP settings problem.  I had 2 Office 365 email accounts synching, one of which was a shared/alias address that used IMAP to connect.  Deleting that IMAP account has stopped the errors.

Adding that shared account to Outlook on a Windows desktop and my iPhone was EASY!  Outlook app for iOS has "add shared mailbox".  Steps are in this article below:

https://support.microsoft.com/en-us/office/open-and-use-a-shared-mailbox-in-outlook-d94a8e9e-21f1-4240-808b-de9c9c088afd?WT.mc\_id=365AdminCSH&ui=en-US&rs=en-US&ad=US

Success with adding the shared account on native Apple Mail on my iPhone:

IMAP ACCOUNT INFORMATION:

Email address: ******@mydomain.org 

(I used to use ******@mydomain.org/sharedboxname)

INCOMING MAIL SERVER:

Host Name outlook.office365.com

User Name ******@mydomain.org

Password is my own password

OUTGOING MAIL SERVER:

SMTP smtp.office365.com

I did not change anything in the SMTP > menu, but here are the settings it defaulted to:

SERVER on

Host Name smtp.office365.com

User Name left blank

Password left blank

USE SSL on

Authentication > nothing selected(!)

SERVER PORT 587

FWIW, after my previous reply (which suggested this was an Apple problem; it was pointed out to me that some users are reporting the same problem on other (i.e., Microsoft) platforms... which I can't address, as I have no devices using MS OS configurations... regardless) I looked into this further, as the problem persisted.

As I am able to send and receive mail, I persuaded myself this had something to do with the certificate in question being related to the use of a web browser (or browsers) on my iPhone and iPad. Speculating that the problem may simply (ha ha) be a corrupted bit of data somewhere in the authentication chain (even a web browser would need to see the certificate if you were retrieving or sending mail via the web on an outlook server), I quit all instances of all web browsers on the devices in question, and rebooted the device. The warnings disappeared.

Further, and I'm sorry if this is redundant information, but you can check on the Trust Certificates installed on your iOS device by going to Settings > General > About and scrolling down to the bottom of the screen where there is a toggle to view the certificates that have been installed.

Tellingly there is no sign of the offending certificate. Also FWIW, the CA of this "rogue" certificate, which is DigiCert, is most certainly on the long list of trusted root authorities that you can look at at this URL on the Apple Support Forums:

List of available trusted root certificates in iOS 12, macOS 10.14, watchOS 5, and tvOS 12

https://support.apple.com/en-us/HT209144

If you are using Windows or some other OS, I'm sure you can find a similar list from those guys.