Security Certificate cannot be verified in Outlook 365

When I start up Outlook 365, I get the message " certificate cannot be verified. The target principal name is incorrect".

However, the certificate is valid. Anyway, I install the certificate successfully. However, the same message reappears when I start up Outlook 365 again.

Screenshots below. Any suggestions how to get rid of the message?

What type of email account do you have configured in Outlook? POP, IMAP,, or Microsoft Exchange?

Is the server domain the same as the email domain?

See for one solution?

The link I posted above is to my personal site and is safe to use, however, I am required to add the following disclaimer when posting on this forum:

Note: This is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.
Diane Poremsky [Outlook MVP]
Outlook Resources:

** I don't work for Microsoft.**
** DO NOT CALL phone numbers received in email notifications.**

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Question Info

Last updated November 24, 2020 Views 1,310 Applies to: