postfix_vmap generated file may lack space

If the real mail host is larger than the internal mail host there may be a space missing between true_addr and addr which create an error in postfix.

I think the error is on line 236 of mta/postfix.py

width = (max(len(alias) for alias in aliases) + len(mlist.mail_host) + 14)

should be

width = (max(len(alias) for alias in aliases) + len(mlist.true_mail_host) + 14)