Problem with SSL for Outlook clients

Question

Problem with SSL for Outlook clients

AleksandarB 66

Hi everyone,
I have newly deployed on premises Exchange environment.
All of the Outlook clients, receive warning messages, about problem with certificate from Exchange servers. Of course, there is installed valid certificate from public authority, however, the error (warning) message from the Outlooks, refers to internal Net-Bios name of the Exchange servers.

Please, how to find the problem,
Aleksandar

Yuki Sun-MSFT 41,451 Reputation points Moderator

2021-12-23T01:39:41.807+00:00

Hi @AleksandarB ,

As based on your description, the certificate issue is more related to the Exchange server side, so I'll add the “office-exchange-server-administration” tag under your thread.

Then before going further, could you remove all sensitive information like the domain name, then share a screenshot of the certificate warning so that we can understand better about your situation?
By the way, does the issue only when you are inside the organization's network?
AleksandarB 66 Reputation points

2021-12-23T14:27:33.14+00:00

Hi YukiSun-MSFT,

In the Outlook dialog box, tries to connect to mail.doman.local, but receives cert from Exchange server.

Answer accepted by question author

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Yuki Sun-MSFT 41,451 Reputation points Moderator

2021-12-23T01:39:41.807+00:00

Hi @AleksandarB ,

As based on your description, the certificate issue is more related to the Exchange server side, so I'll add the “office-exchange-server-administration” tag under your thread.

Then before going further, could you remove all sensitive information like the domain name, then share a screenshot of the certificate warning so that we can understand better about your situation?
By the way, does the issue only when you are inside the organization's network?
AleksandarB 66 Reputation points

2021-12-23T14:27:33.14+00:00

Hi YukiSun-MSFT,

In the Outlook dialog box, tries to connect to mail.doman.local, but receives cert from Exchange server.

Answer 1

One of your client virtual directories isnt set correctly to the FQDN that matches a subject name on the cert.

Run this from Outlook:
https://answers.microsoft.com/en-us/msoffice/forum/all/mailboxes-test-e-mail-autoconfiguration/19f9c90a-4640-46c4-a574-dbec29bdb8ba?auth=1

Then click on the XML tab in the results and check the URLs returned. See what they say for the results checking the <Protocol>

you can post here minus any personal data as well ( copy and paste from the XML section

Did you set the correct autodiscover URI?

Example:

Set-ClientAccessService -Identity "MBX-01" -AutoDiscoverServiceInternalUri "https://mbx01.contoso.com/autodiscover/autodiscover.xml"

https://learn.microsoft.com/en-us/powershell/module/exchange/set-clientaccessservice?view=exchange-ps

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Problem with SSL for Outlook clients

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