Validate passwords entered for smarthost and notifications
It appears that passwords of a certain length or containing certain characters are not properly handled by Sophos when it attempts to authenticate with a smarthost. The result is that Sophos cannot authenticate with the smarthost and outbound e-mails remain stuck in the spool, showing as failed. There is no indicating in the logs accessible in the GUI that the problem is an authentication error.
It might save users some frustration if Sophos were to either include validation logic to reject problematic passwords when they are entered and/or including a note or tip in the GUI indicating the applicable parameters for such passwords.
I should perhaps note that this only applies to versions after 17.1.4. I encountered this issue as I previously had used a long, complex password (35 characters) for the smarthost, which resulted in authentication errors when I updated to a later version of the firmware. It worked just fine in 17.1.4 and previous versions.