Hi,

We have an internet gateway machine which is also running vpop3 email server. We want to connect this to our WAN in turn. But there is a problem such that if we specify the default gateway to our router, internet connection does not. Is there a way of resolving this problem such that we have internet connection and at the same time we are able to connect to other branches through the WAN?

Yes. You will need to specify multiple routes in your router.

For example:

Internet gateway: 192.168.1.1 (default gateway)
WAN router: 192.168.1.2
Site 1 Network: 192.168.2.0/24
Site 2 Network: 172.16.0.0/16

In your Internet router, you will need to add two static routes for the two sites and the gateway for each of these will be 192.168.1.2.