I have two SRP521W.
One in HeadQuarters (HQ) and one in Branch Office (BO). Both have Static Public IP
Site-to-Site VPN connection is estabilished between them. VPN works.
In HQ we have mail server. When main internet connection fails backup connection starts on 3G modem. VPN on 3G modem is working. But we have problems with emails. If main internet connection fails in HQ we dont get any emails. 90% of sent emails are delivered through 3G - 10% are blocked by
recipient email servers (blocked as spam - IP not equal to our MX).
So I figured out to forward emails through our second static IP in Branch Office and add this IP to DNS as MX with lower priority.
1. How to configure Branch Office SRP521 to forward port 25 to server in HQ using VPN tunnel.
2. How to configure HQ SRP521 to forward port 25 to router in our BO. All remaining traffic (http) should go out through 3G modem).
Branch Office local router IP is 192.168.4.1
Assume Branch Office Public IP is 188.8.131.52
HQ local router IP is 192.168.1.1
email server local IP is 192.168.1.2
Assume HQ Public IP is 184.108.40.206
in BO (branch office) I created NAT forward port 25 to 192.168.1.2 - but it doesnt work.
What else should I configure.
Greetings, Szymon Polok