For now, Microsoft can only recommend using a complicated workaround as it preps a fix.

There is no fix available, but you can always revert to an older version.

A new Outlook (Classic) update is preventing Windows users from opening encrypted emails. Microsoft confirms the bug and ...

A new Microsoft-issued software patch for Outlook (Classic) on Windows 11 inadvertently broke encrypted email support - ...

Microsoft has confirmed a known issue that prevents recipients from opening encrypted emails in classic Outlook.