Script options for migrating mailboxes from Exchange 2003 to Exchange 2010
I recently came across a customer query of migrating mailboxes from Exchange 2003 to Exchange 2010 via a script. Sharing the options that I had discussed with him
(There could be more so please share your comments 
)
Option1
1. Create a text file with the alias of each Exchange 2003 mailbox that you want to move to Exchange 2010 per line saved as C:\Temp\ListOfExchange2003MailboxAlias.txt
2. Put the following in a text file with a .ps1 extension for example Exchange2003MailboxMoveRequest.ps1
a. Foreach ($Exchange2003Mailbox in (Get-Content C:\Temp\ListOfExchange2003MailboxAlias.txt)) {New-MoveRequest -Identity $Exchange2003Mailbox -TargetDatabase ReplaceWithExchange2010MailboxDatabase}
3. Use Task Scheduler to schedule the script to run at whatever time you want
Option2
Option 3
For increasing parallel migrations
1. Configuration file change to increase parallel migrations - https://markswinkels.nl/2011/04/migrate-mailbox-from-exchange-2003-to-exchange-2010/