Subject: undelivered mail returned to sender
this is the postfix program at host correio . quick . com . br .
i ' m sorry to have to inform you that the message returned
below could not be delivered to one or more destinations .
for further assistance , please send mail to
if you do so , please include this problem report . you can
delete your own text from the message returned below .
the postfix program
: user unknown . command output : invalid user
specified .