Because of an ADSL line upgrade we were forced to change our router, from Juniper back to our "old" Draytek Vigor 2800G

I plugged in the "new" router, set up the ISP username and password, gave it the right internal IP address (A.B.C.2) and hey presto, we were on the internet again, and VoIP was working.

However, our Exchange mailserver, on the SBS server at A.B.C.253, while able to send mail out, was not collecting any external mail.

We got 5 static IP addresses from our ISP, viz:

" * the network address is: X.Y.Z.192
* your router/hub address is: X.Y.Z.198
* your subnet mask address is: 255.255.255.248 if you have 5 Static IP addresses or 255.255.255.240 if you have 13 Static IP addresses
Your computers can use addresses from X.Y.Z.193 to X.Y.Z.197 "

In DNS our mailserver is set to X.Y.Z.193, but the router is X.Y.Z.198

Someone on another forum told me to forward port 25 being received on x.y.z.193 to a.b.c.253.

I looked at the Port Forwarding table on the Draytek, and there already is an entry, called SBS-EXCH, which redirects any TCP traffic on port 25, to A.B.C.253, port 25.

what else am i missing?
cheers in advance

I think I know what was missing!!

The router didn't know that it was acting as an access point for a RANGE of IP addresses, it thought it was only acting as ONE IP address (the router IP address X.Y.Z.198).

In the router config pages:

Internet Access > PPPoE / PPPoA > IP Address From ISP > WAN IP Alias > <fill in all the other static IPs!!>

As the manual says:

WAN IP Alias - If you have multiple public IP addresses and
would like to utilize them on the WAN interface, please use WAN
IP Alias. You can set up to 8 public IP addresses other than the
current one you are using.

I added in the other static IP addresses that we are leasing from our ISP, including the one that our mailserver is using, and lo and behold! mail started arriving in our inboxes !!!

ONe question, should I tick the box "Join NAT IP Pool" at the end of each line in the "WAN IP Alias" field ?

Leave join NAT IP pool unticked otherwise the router will use that IP for general internet access which tends to mess up HTTPS connections if it switches between IPs.

thanks voodle!

I didn't want to change this setting as things seemed to be working "if it ain't broke don't fix it" IIABDFI ? lol.
As it happens we did start to have problems with a banking site after switching routers. I remembered this post so came back to it and discovered your solution. So many thanks....

note to self... MultiNAT is mapping internal IP addresses (...NAT) to >1 (...multi) external IP addresses.

see also:
http://www.draytek.co.uk/support/kb_vigor_multinat.html