It looks like the Shared Mailbox Creation template by default pulls information from what is put initially in the Display Name field in the template.

This probably shouldn't be setup like this since for us we tend to put spaces for our mailbox Display Name. This in turn conflicts with the smtp and alias fields as it attempts to auto populate them from what's entered from the Display Name field. Those fields don't allow spaces in exchange.

There should be a logon field added to the template like in the Exchange management Console. Then there should be an option to populate the smtp and alias fields from that attribute instead of the Display Name field.