Temporarily suspend incoming mail for one user

[Brian Huffman]

I'm migrating to a new mail server and I want to suspend incoming mail 
for just one user.  Is there an easy way to do it?

We're migrating a few users at a time, so after the migration I intend 
to create an alias for the user that goes to the new server. But I want 
to make sure that the mailbox is consistent during the migration.

Thanks,
Brian