When a message cannot be delivered to someone in your
organization, that person will receive a non-delivery
report (NDR). All NDRs in your organization will be sent
with the SMTP postmaster's address in the From line.
Therefore, whenever someone replies to an NDR, either to report the
delivery failure or to seek help in diagnosing the situation, this
is the account that will be contacted.
For this reason, you should use an alias that will proxy replies
to someone, or a valid SMTP e-mail address, such as
user@<domain>.com, where <domain> is your
organization's default domain. Internet users who get an NDR will
then be able to reply to it and contact someone who can help them.
At the very least, your organization will be made aware of the