Verification of Sender Information
Much of the spam that is sent on the Internet today is stamped with a
bogus sender address. To help prevent this sort of spam, all modern
versions of sendmail do two things to check sender addresses.
- The sender address must have a username portion and a
domainname portion. Mail will not be accepted from user
roth, but it will be accepted from user
roth@uiuc.edu. To disable this extra checking, use
the FEATURE(accept_unqualified_senders) directive.
- The domainname portion of the sender address must be resolvable with
the DNS. To disable this checking, use the
FEATURE(accept_unresolvable_domains) directive.
Mark D. Roth <roth@feep.net>