We are using vendor based antispam filtering. Connectors are on place, transport rules or on place, MX and Spf records updated its working great. But it can be bypassed in one or two ways which makes us not having complete protection. To avoid this situation i have created a transport rule in exchange which will drop everything which is not coming our anti spam filtering smart host and added a except condition for calendaring items so that calendar invites shouldn't get rejected. My only issue is with this rule enabled will it effect printers configured in the organization ? will it drop printer or scan to email jobs ? Our printers are configured using a connector to send mail using 365 smtp relay according to Microsoft 365 configuration manual. or these printers are inside the network using private IPs this rule wont effect this. I am new to this, not so technical. Please Help this is the last piece missing from delivering the antispam project.