You may want to change your IP address in case of an IP address change of your mail servers. Also when you change your ISP. Here are the steps for changing or adding an IP to your Postini Administration Account:
1. Go to https://login.postini.com and login to your Authorized Admin Postini Account.
2. On the upper left corner, click on 'Show Hierarchy'.
3. From the list, click on the '<Your Org> Email Config' link.
4. Click on 'Inbound Servers' tab at the top and then click on 'Delivery Mgr' from the sub-tab at the top.
5. You can see the current IP addresses in the graph legends. To change those IP's click on 'Edit' just at the top of that graph.
6. Under Use My Own Email Server, you will see your current IP's. To change them, edit and replace those IP's with the newer IP's.
7. You can specify more than one IP for Load Balancing your email data. Once done entering the new IP, click submit.
8. Your new emails will now be delivered to your new IP by Postini.