I have a user with a 30G mailbox. He was on Exchange 2003. He then went out and bought a mac with Outlook 2011. Since he was on Exchange 2003, it was not compatible. Unfortunately his office did not have an Exchange 2010 so I had to move him across the WAN to another office. He is unhappy with the performance so I would like to move him another mail server closer geographically. My question is, it took 36 hours to move his mailbox from 2003 to 2010. I have read that I can move a 2010 mailbox across servers without interruption to the user. However due to the fact that his original mailbox was on 2003, will that be a problem?