We like to call MimeCast MineCraft around here, like that blocky game you know

Anyways,

This is a nice microsoft article on the steps

http://technet.microsoft.com/en-us/library/bb124953(v=exchg.65).aspx

Setup ‘Allow automagic forwarding for our *.domain.com

Enable Envelop Journaling

Created a new mailbox store for the journal account (per recommendation)

Create new MimeCast journal email account

Setup server side forwarding

Setup recipient policy to clear out the deleted box

Configured Exchange to archive all the mails to mimecastjournal

Now to finish config with mimecast