I am install new windows 2012 standard server and Exchange 2013 new domain name.  I have a different domain that I want to migrate user mailboxes on a Exchange 2003 server.  would anyone have suggests on where to start?

Migration from 2003 to 2013 isn't supported, therefore you can do a double upgrade 
-> Exchange 2003 to Exchange 2007/2010 
-> Then Migrate to Exchange 2013

Example.
1. Migrate from 2003 to Exchange 2010 SP3
https://www.simple-talk.com/sysadmin/exchange/upgrade-exchange-2003-to-exchange-2010/

2. Cross Forest Migration to Exchange 2013 with CU1

Hi

Any update on this issue?

Cheers

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