Answer
The "WebMailLogoffURL" variable is a URL the user is directed to when they click on the Logoff button.
The "WebMailLogonURL" variable is a URL the user is directed to when they have been logged off by the session timeout.
The "WebMailLogoffURL" should work at a user or domain level as the system knows who the person was before the logoff as well as at the system level. However "WebMailLogonURL" has no idea who the user is and only works at the system level.
See Also:
Keywords:WebMailLogoffURL WebMailLogonURL