An inbound mail gateway is a server through which all incoming mail for your domain passes. The Postini servers are an example of an inbound mail gateway: they filter (and possibly archive) incoming mail before passing it on to the Google Apps mail servers.  You'll want populate Google Apps inbound gateway with Postini server IP's. 



Google Postini IP Ranges


System IP Range CIDR Range IP/Subnet Mask Pair
5, 6, 7, 8, 20 64.18.0.0 - 64.18.15.255 64.18.0.0/20 64.18.0.0
mask 255.255.240.0
9 74.125.148.0 - 74.125.151.255 74.125.148.0/22 74.125.148.0 
mask 255.255.252.0
10 74.125.244.0 - 74.125.247.255 74.125.244.0/22

74.125.244.0 
mask 255.255.252.0

 

11, 20, 200, 201 207.126.144.0 - 207.126.159.255 207.126.144.0/20 207.126.144.0
mask 255.255.240.0


How do I know which system we are on? -  


Take a look at the URL after signing into the Administration Console, it is indicated in this screenshot , I'm on system 7.