we are planning an exchange 2003 transition to 2007 or 2010.
I am doing a lot of researches ; I know exchange 2003 and 2007/2010 can co-exist in an enviornment for some time until we start moving mail boxes from 2003 to 2010 and switch MX records to new exchange server .
Problem : some of the mail boxes are huge (>3 GB) , our new exchange server will be in a data center with a 10 MB MPLS link to current 2003. so .. we thought that we export mail boxes with Xmerge , copy them on an external hard drive and import them into new enviornment .
here are my concerns :
Can I start making user mail boxes (instead of migrating them) on 2010 exchange while 2003 is still handling email tasks ? so that I have a complete set of mail boxes ready for PST imports on the day that we will change MX records ?
From on-line discussions that I've had , it seems that it might create some email issues in the enviornment when two mailboxes are present fora given user. ( one in 2003 and one in 2007)