SophosXG v19 ((home) - redirect Mail requests to an external (open source) secure mail gateway

Hello Community,

if upgrade to SophosXG v19 (Home Edition) and it takes a view minutes, but is was well done.
now i would like to scan/monitor the form/to sender and the definition of "white/gray/black" listet mails that are coming trough SophosXG
I've no internal Mailserver and no Sophos Central in place. An SSL Certifikate from my external FQDN can be served for this solution,

My challange
How to configure SophosXG to redirect all out-/ingoing requests trough the mail ports in the 1st steop to my SMG in the extranet to filter the mail traffic ? My Client connection is always established from the LAN to the WAN when the client is running. There is no DNAT in place.

Does anyone here have an idea how/if to configure this in the SophosXG

Thanks to all in advance.

Added TAGs
[edited by: emmosophos at 7:38 PM (GMT -7) on 23 May 2022]