WHM / Cpanel migrating

Hey,

My company has a server whose name is server1.domain.net. The server
has WHM / Cpanel. We are thinking of migrate to another server to support PHP5. . We have about 60 accounts on current server. We want to migrate all of the accounts onto the new server one by one. This means the current server and new server will have to run concurrently for months. We want to name the new server to server2.domain.net. all of our account user's email are using mail.domain.net as their POP and SMTP server. Will the new server name cause any problem? With our situation, what we need to look out to avoid clash between 2 servers?

Thanks a lot in advance!

Blessings,
Rocky