I have a virtual domain setup. As usual, accounts of virtual may be
either a mail storage or an alias.
It is possible to qualify aliases which haven't domain to the virtual
domain of the account generating the expansion.
I mean, if I'm going to deliver to foo@???, and address data
expands to 'fooalias', then deliver to fooalias@??? instead of
fooalias@<qualify_recipient option>.
