Outlook: There is a problem with the proxy server's security certificate. The name on the security certificate is invalid or does not match the name of the site. Outlook is unable to connect to this server.

Issue: Error message from Outlook: There is a problem with the proxy server's security certificate, %s. The name on the security certificate is invalid or does not match the name of the site. Outlook is unable to connect to this server. (%s)
  
Finding/Resolution: Checked Outlook provider settings and saw that server and certificate was set to 2 dashes(--)

used this command to fix: set-outlookprovider EXPR -Server $Null and Set-Outlookprovider EXPR -CertPrincipalName $Null

The command will set outlook provider EXPR to Null(Blank). By doing so Outlook will rely on autodiscover to get the correct outlook anywhere settings