we have an old Exchange 2007 hosting an email domain. Now the company has changed domain and we setup a new Exchange 2013 on the new domain that is up and running. About the old Exchange 2007, I'd like to switch it off, but mantaining the domain active and moving a few mailboxes on the new Exchange 2013. So, I will tell to 2013 that it is tenant of the old domain, but about the mailboxes to transfer, what do you suggest to do? Is there a simple way (programmatical if possible) apart from exporting the .pst file and re-importing it on the new mailbox? Thank you
It isn't clear what you mean by "domain" in your question, as they can have two meanings with regards to Exchange. Have you just changed the email domain, so Exchange 2007 and 2013 can see each other. Alternatively, have you built a completely separate WINDOWS domain/forest and therefore the servers cannot see each other?
If the former, then just move mailboxes. If the latter, you have two options.
PST migration. For a small number of mailboxes this is probably the easiest method. Export to PST, import to the new mailbox, adjust X.500 values so everything works.
Cross forest migration. That will require a trust between the two domains and some other work. For a small number of mailboxes not usually worth the hassle. It isn't what I would call simple though, because a lot of things have to be correct for it to work correctly.