Internet Services Delta Manual for HP-UX 11i Version 1.6

Spam Control Using MSA (RFC 2476)
Message Submission Protocol is a means for MUAs to introduce new messages into the message
transfer agent routing network. Messages being submitted by MUAs, in some cases, may be
unfinished. Unfinished messages need to be completed by the MSA before submitting to the MTA.
It also helps in implementing authenticated submission, including off-site submission by authorized
users such as travellers.
The messages received on port 587 are regarded as "submitted messages". MSAs may implement
message rejection rules, i.e. if an MSA is unable to determine a return path for the submitting user,
from a valid MAIL FROM, a valid source IP address, or based on authenticated identity, then the
MSA will immediately reject the message, as it gives the user and MUA direct feedback.
Sendmail 8.11.1 supports RFC 2476, a protocol for message submission. The anti-spam rulesets
have been enhanced to improve the anti-spam capabilities. The RFC proposes a new standard for
the Message Submission Agent (MSA). This is designed to replace the more general-purpose mail
transfer agent (MTA) as the first service to which a Mail User Agent (MUA) connects to deliver a
mail message. The RFC also describes how the usual protocols for SMTP service should be tightened
up at the point where mail enters the system, rather than being routed from one site to
another.Sendmail 8.11.1 also serves as a powerful tool to authenticate and control mail messages.
By default, MSA is defined in the sendmail.cf file as:
O DaemonPortOptions=Name=MSA, Port=587, M=E
where Port 587 is reserved for email message submission.
A Message Submission Agent still uses all of the same rulesets for processing the message (and
therefore still allows message rejection via the check_* rulesets). In accordance with the RFC, the
MSA will ensure that all domains in the envelope are fully qualified if the message is relayed to
another MTA. It will also enforce the normal address syntax rules and log error messages. In
addition to the above, you can request authentication before the messages are accepted by MSA
by using the M=a modifier in the DaemonPortOptions.
NOTE: MSA can be turned off in the sendmail.cf file using the option, 'no_default_msa' in
gen_cf. For more information, refer to "no_default_msa" option below.
The XUSR SMTP command as well as the'-U' (initial user submission) command line option are
deprecated. Mail user agents are expected to start using MSA for initial user message submission
from now onwards. XUSR may be removed in future releases. The next release of sendmail will
assume that any message submitted from the command line is an initial user submission and act
accordingly.
Generating the Configuration File
gen_cf is a UNIX shell script, which is installed in the '/usr/newconfig/etc/mail/cf/cf' directory.
This script cannot be copied to a different directory and executed, as it uses the macros defined
in the /usr/newconfig/etc/mail/cf directory to generate the sendmail.cf file.
This script provides many options that will enable a specific ruleset. The input file for this script will
be the *.m4 files defined in the /usr/newconfig/etc/mail/cf directory. The user can specify
the output file and later incorporate site-specific changes (if any) in the output file.
NOTE: The output file generated by gen_cf, sendmail.cf.gen can be later copied or moved to
/etc/mail/sendmail.cf file.
IMPORTANT: The entries in the sendmail.cf file preceded by a '#' (hash) are commented by
default.
In addition to the options provided in Sendmail 8.9.3 release, the following new options have
been added in the gen_cf script:
8 Sendmail 8.11.1