Complete block of M365

This morning all of our clients (located behind a Sophos Firewall with active DNS Protection configured) were unable to access ANY service of M365.

  • No eMail
  • No Teams
  • No Sharepoint

After we've searched all the firewall logs, didn't find anything, we've changed the dns settings to standard Google ( and it worked again instantly.

Are there any known issues with Sophos DNS Protection ?