Hi, we are encountering a strange error when opening MS Outlook.
We recently had issues with mails not being delivered and when our ISP was troubleshooting the issue they told us that our problem was that we are sending through our excahnge server with the ip x.x.x.4 while when you resolve our name mail.company.xyz the resolved ip was x.x.x.5
So the told us to switch the A record to x.x.x.4
Ever since then when we start Outlook we get a certificate error, what is really strange is that the certificate Outlook doesn't like is shwoing that it comes from the Sophos firewall and not the Let's Encrypt certificate that we use for our exchange server.
We switched back to the old IP / A-Record configuration but the error remains.
When i open OWA (https://mail.company.xyz/owa) i can see the Let's encrypt certificate, the way it should be. Why would Outlook use the Sophos certificate instead of the exchange server certificate? I'll add screenshots below.
Sophos Firewall is acting as an MTA. No Sophos Central E-Mail Protection in place.
This is the Outlook error:
This is the certificate i get when i open OWA in a browser:
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