@cbareis
Strange. Chrome and Edge work as expected. Firefox (and Opera) are blocked by Bitdefender. Certifcate for exchange.opera.com is certainly neither expired nor revoked; IMO Bitdefender is at fault here.

I would contact both Opera and esp Bitdefender support, Opera issue can be reported from O menu - Help - Report an issue..., most likely Bitdefender has some feedback page either.