In an organization or any kind of business if you are thinking to upgrade from your exchange server 2003 to exchange 2010 instead of this its better to move to cloud based office 365 service. Before performing migration you need to understand your entire exchange server and the number of mailboxes that needs to be migrated.
To perform exchange migration reliably and effortlessly you can check out EdbMails Exchange Migration tool which does your job flawlessly. The best part about this tool is you can get it free. Using free trial version you can migrate 30 items from each and every folder.