Sendmail 8.9.3 Release Notes

Chapter 1 21
New and Changed Features
New Features
Setting this option, will allow relaying of all those mail messages
where the sender of the mail messages is a valid user on that
machine. For example, if abc is a valid user on host 1 then, user
cbz on host 2 can telnet to host 1 as user abc and then send mail to
user xyz on host 3 i.e. host 1 is now relaying.
This should only be used if absolutely necessary as it opens a
window for spammers. Specifically, they can send mail to your
mail server that claims to be from your domain (either directly or
via a routed address), and you can then go ahead and relay it out
to arbitrary hosts on the Internet.
This feature is commented in the default sendmail.cf file. To
enable this feature use the gen_cf script distributed with the
sendmail-8.9.3 patch.
— Relay base on MX records
Setting this option, will turn ON the ability to allow relaying
based on the MX records of the host portion of an incoming
recipient; that is, if an MX record for host foo.com points to your
site, you will accept and relay mail addressed to foo.com.
This feature is commented in the default sendmail.cf file. To
enable this feature use the gen_cf script distributed with the
sendmail-8.9.3 patch.
— Loose relay checking
Setting this option, will turn OFF the default behaviour of
rechecking all those recipients using % addressing.
For example if the recipient address is user%site@othersite then,
the default behaviour without the above feature ON is that
Sendmail will check if other site is an allowed relay host specified
in either class ’R’ macro or access db file. If yes then, the
check_rcpt ruleset will strip @othersite and recheck user@site for
relaying. This rechecking will not be done if this feature is turned
ON. This should not be needed for most installations.
This feature is commented in the default sendmail.cf file. To
enable this feature use the gen_cf script distributed along with
the sendmail-8.9.3 patch.
• Better checking on sender information
As of version 8.9, sendmail will refuse mail if the MAIL FROM:
parameter has an unresolvable domain. If you want to continue to