SMTP Rule doesn´t work

Hi, 

I use a Sophos with 18.0.5 with MR-5.

There I want to configure the SMTP Rule for my Exchange. 

In secured Domain (Geschützte Domäne) I add my domain.

For error analysis I have disabled the other options.

Do you have any idea what it could be, that no emails are arriving.

Now I use a simple Portforwarding, because that works...

Thanks!