If you have a BES in the US, you're going to want to check your SRP configuration on the BES to make sure it will still work properly after May 28. RIM is changing some IP addresses that will affect your users.
First off, check the BES configuration and make sure that the Blackberry Router configuration is pointing to
us.srp.blackberry.com and not another host name. Next, run the SRP test and make sure that you see that a successful connection is made to the following new IP addresses:
126.96.36.199. You will likely see two other addresses tested - those are being retired.
Depending on your firewall configuration, you may need to update it to allow traffic over port 3101 to those addresses. A better configuration would be to allow traffic based on these recommendations from RIM. That way you'll be ahead of the curve if a change is made in the future.