Authentication prompt on Shared mailbox which seems public folder mailbox issue

Question

Environment: Exchange Hybrid, users, shared mailboxes and public folder mailboxes are On Premise

We have the following autodiscover url, the DNS records are there too:

1. Users have no issue opening their mailbox. Autodiscover works fine, you see the url in the outlook client.
2. Only users with shared mailboxes get and authentication prompt lately (see below). But shared mailboxes have no credentials so it's not logical. When you delete the shared mailbox name and you put in your own credentials with password then the issue is temporary resolved. For this profile, for this machine
3. Logon on another fresh machine it's starts again with the popup

If you cancel this message you get the following autodiscover prompt, notice that the root issue comes from the

first public folder mailbox (primary hierarchy). And notice it doesn't give back the right autodiscover url. It gives back one of our Exchange servers, with the autodiscover.xml

English: Do you want to allow this website to configure server settings for pfmailbox@domain.nl

We see the issue with every user who has shared mailboxes and has a public folder.
Has someone got an idea how to fix this. The issue came to light after change Licenses E3 to E5, but this has nothing to do with that change.

Thank you.

Kind regards,

André

Answer 1

Hi @ André Borgeld ,

 

Allow this website to configure server settings?

 

According to my search, this warning is a feature of Outlook that retrieves the Autodiscover profile and checks if it is extracted from the correct domain and accepted.

Have you tried selecting the option "Don't ask me again about this website" to see if anything helps?

 

If you still keep popping up and cannot send and receive emails normally, please refer to the following link to run Test E-mail AutoConfiguration:

Mailboxes - Test E-mail AutoConfiguration - Microsoft Community

(Note: Microsoft provides third-party contact information to help you find additional information about this topic. This contact information may change without notice. Microsoft does not guarantee the accuracy of third-party contact information.)

Also note that run the test after clearing the “Use Guessmart ”check box and the “Secure Guessmart Authentication” check box.

You can also share screenshots under the log tag after masking your personal information for us to research.

 

Additionally, the official documentation here provides an article that suppress Autodiscover redirect warnings by setting registry values：

How to suppress AutoDiscover redirect warning - Outlook | Microsoft Learn

 

Hope the above information is helpful to you!

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Answer 2

Thank you @Aholic Liang-MSFT i will do that, when it pops up again.

Because I've logged in with credentials it doesn't pop up at the moment. I will keep you informed.

Kind regards,

Andre