we do not relay for this domain

For problems with incoming mails:
The domains for incoming mails have to be configured in the Admin Webinterface -> Configuration -> E-Mail Transport -> Local Domains.
You must restart the SMTP-server after the entry (alternatively you can reboot the appliance)!
 
For problems with outgoing mails:
The sending mail server must be registered in the admin Webinterface -> Configuration -> E-Mail Transport -> trusted Networks.
Immediately after the registration the SMTP-Server must be restarted.
Please mind the subnet mask matches to the IP address or the host name.
 
Example:
- individual hosts release (recommended):
network: 192.168.0.4
subnet mask: 255.255.255.255 ( 4 x 255!)
 
- all subnets:
network: 192.168.0.0 (0 as last!)
subnet mask: 255.255.255.0 ( 3 x 255!)