Originally Posted by Mightypants
Also, are there any issues configuring a new BES Server while the old one is still active when it comes to SRP etc...?
Yes. If you plum up the BES services on the new server while the old one is online, it will disconnect the new BES from RIM's network in 5 seconds (I think thats what corey or grey or someone said before). If you do not start the services, then you are safe.
Also, adding a user to two BES servers within the same Exchange organization while both BES servers are up and running will most likely result in a bit of damage to the user's mailbox. I had to reboot the BES server before I could get back into my account when performing this process. It filled up our Exchange server's secondary drive due to log files increasing in size with errors within 24 hours, also. BAD idea unless the first BES just crashes and you have to move the user to a second BES. Everything said in this paragraph pertains to TWO BES servers running TWO SEPARATE SRPs, btw.
If I were you, I'd just build the new BES server w/o starting up its services. Shut down the old BES server and then bring up the new one with the same SRP. It should (from experience, if memory serves me correct) bring up the userlist already intact and no one suffers any issues. If you have the database local, you will want to go through the database migration process as well. There are a few topics on both subjects (together and separate), so do some searching and I'm sure you'll find a thread with the details in them.