Invalid Security Certificate in Exchange

Question

I get ths error message appears whenever anyone on our system opens outlook:

I know very little about our Exchange server but was told that it was once configured differently and from what I've read it is a matter of going into the exchange shell and remove our exchange server from issuing the certificate but I am weary of changing anything on the system that I am unfamiliar with. I wanted to get some experts eyes on this and see if this indeed seemed to be the proper solution. Thank you in advance.

Answer 1

The certificate issued to Exchange does not have a SN or SAN that matches the FQDN the Outlook client is configured for. Your outlook clients are configured for mail.companyname.com, and your certificate is issued for something different (eg exchange.companyname.com, which obviously doesn't match).

You need one of two things:

• The certificate on the Exchange server needs to be reissued and installed to match what the Outlook clients are configured to connect.
• The Outlook clients need to be configured for what the Certificate says, which might also entail configuring DNS and/or Exchange to respond to this name as well (depends on what has already been done). Configuring the Outlook clients might also be done through Exchange, depends on what version you're running and how Exchange was setup.

Some of these are easier than others, and much of that depends on what version of Exchange and Outlook you are running as well as where you're getting your certificates from.