SMTP - Restrict In and Outgoing Traffic to dedicated Interfaces/IPs

This recommended Read should be helpful: https://community.sophos.com/xg-firewall/f/recommended-reads/122602/sophos-xg-how-to-setup-mta-mode-when-you-have-multiple-wan-ports-or-alias-ip-addresses

And another unclear fact: I expected the route prio according to the gateway wights. But this is not true. GW 1 is wight 1, GW 2 is weight 10. But in 9 of 10 times GW 2 is used...

The SMTP Log (GUI) allways shows outgoing IP as "" (empty) for outgoing mail. Not very helpfull.

And another unclear fact: I expected the route prio according to the gateway wights. But this is not true. GW 1 is wight 1, GW 2 is weight 10. But in 9 of 10 times GW 2 is used...

The SMTP Log (GUI) allways shows outgoing IP as "" (empty) for outgoing mail. Not very helpfull.

Weight is not Prio. See: https://docs.sophos.com/nsg/sophos-firewall/18.0/Help/en-us/webhelp/onlinehelp/nsg/sfos/concepts/LoadBalancingWeights.html

You need to configure a extra WAN Gateway for your Alias and configure a IP Host for the SNAT. 

thanks for answer.

What does it mean in detaill:

"You need to configure a extra WAN Gateway for your Alias and configure a IP Host for the SNAT. "??

Take a look at the Recommended read: https://community.sophos.com/xg-firewall/f/recommended-reads/122602/sophos-xg-how-to-setup-mta-mode-when-you-have-multiple-wan-ports-or-alias-ip-addresses

The SNAT should reflect your needed MASQ. 

I changed the LAN IP for the server lan become the main address.

Reading https://community.sophos.com/xg-firewall/f/recommended-reads/122602/sophos-xg-how-to-setup-mta-mode-when-you-have-multiple-wan-ports-or-alias-ip-addresses the last add is: Reboot the system. So is this really needed?