I'm trying to properly plan staging our current physical environment with a pair of clustered 2007 boxes and two CAS servers. With that said we have no policy in place to control mailbox sizes and some users have 40gig mailboxes. Do we have to shrink these and how? Same goes for database sizes do we have to offline maintenance them? We also have several oversized Storage groups. Essentially I'm looking for assistance on what to do prior to migrating to Exchange 2013.

thanks,

Hi Chicojr,

Thank you for your question.

Do we have to shrink these and how?

A: we could not shrink the mailbox, just move it to Exchange 2013 mailbox server.

Same goes for database sizes do we have to offline maintenance them?

A: we could move the database to Exchange 2013 and not configure offline maintenance mode. But we suggest you move database out of production time.

Essentially I'm looking for assistance on what to do prior to migrating to Exchange 2013.

A:what we will consider, we could refer to the following link:

http://blogs.technet.com/b/meamcs/archive/2013/07/25/part-3-step-by-step-exchange-2007-to-2013-migration.aspx

We could  refer to the following link to update Exchange 2007 to Exchange 2013:

https://technet.microsoft.com/en-us/library/jj898581%28v=exchg.150%29.aspx

If there are any questions regarding this issue, please be free to let me know.

Best Regard,

Jim

Why don't you check video tutorial for Ex2007 -> Ex2013 Migration-

https://www.youtube.com/watch?v=3yAwNt6yGr4
https://www.youtube.com/watch?v=2OWoSfKNmGI

As above suggested you can not shrink the size of mailbox, the best way to get this done is to create a new DB and move them to it.
I found an informative article on how to migrate from Exchange 2007 to Exchange 2013 including planning and configuring co-existence : http://www.msexchange.org/articles-tutorials/exchange-server-2013/migration-deployment/planning-and-migrating-small-organization-exchange-2007-2013-part1.html

If you want to migrate users mailboxes automatically, this automated tool http://www.exchange2007to2013migration.exchangemigrationtool.com/ can also be a nice alternative approach that provides the way to perform migration task flawlessly.