The load balance policy can be used to force outgoing SMTP mail to use a particular WAN port. This is required when both WAN ports are active on the router but are connecting to different service providers and the mail server is associated with one service provider only and will be rejected if coming from another connection.
In the settings below we have SMTP mail going through WAN1.
- Src IP Start is left blank since we want all PC’s to send mail via WAN1.
- Dest IP setting is the service provider IP
- Dest Port is the SMTP port used
Go to WAN >> Load-Balance Policy configuration menu