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58 lines
2.8 KiB
Plaintext
58 lines
2.8 KiB
Plaintext
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Sendmail Processes
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As of sendmail 8.12, in order to improve security, the sendmail binary no
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longer needs to be set-user-ID root. Instead, a set-group-ID binary
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accepts command line mail and relays it to a full mail transfer agent via
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SMTP. A group writable client mail queue (/var/spool/clientmqueue/ by
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default) holds the mail if an MTA can not be contacted.
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To accomplish this, under the default setup, an MTA must be listening on
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localhost port 25. If the rc.conf sendmail_enable option is set to "NO",
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a sendmail daemon will still be started and bound only to the localhost
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interface in order to accept command line submitted mail (note that this
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does not work inside jail(2) systems as jails do not allow binding to
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just the localhost interface). If this is not a desirable solution, it
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can be disabled using the sendmail_submit_enable rc.conf option. However,
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if both sendmail_enable and sendmail_submit_enable are set to "NO", you
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must do one of two things for command line submitted mail:
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1. Designate an alternative host for the submission agent to contact
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by altering /etc/mail/freebsd.submit.mc (or setting SENDMAIL_SUBMIT_MC
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in /etc/make.conf to an alternate .mc file) and using
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'make install-submit-cf' in /etc/mail/. Change the FEATURE(msp) line
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to FEATURE(msp, hostname) where hostname is the fully qualified hostname
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of the alternative host.
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Or:
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2. Return to using a set-user-ID root sendmail binary by changing the
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ownership and permissions on the sendmail binary and removing the
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/etc/mail/submit.cf file:
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chown root /usr/libexec/sendmail/sendmail
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chmod 4755 /usr/libexec/sendmail/sendmail
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rm /etc/mail/submit.cf
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If you install from source, set the SENDMAIL_SET_USER_ID flag in
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/etc/make.conf.
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Also, as of 8.12, a new queue-running daemon is started to make sure mail
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doesn't remain in the client mail queue. By default, it simply runs the
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client mail queue every 30 minutes. Its behavior can be adjusted by setting
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the sendmail_msp_queue_enable and sendmail_msp_queue_flags rc.conf options.
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Filtering out SPAM from your site
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Sendmail now includes excellent tools to block spam. These tools are
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available as FEATUREs that you can add to your site's .mc file. Proper use
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of these FEATUREs will prevent spammer from using your site as a relay as
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well as significantly decrease the amount of spam that arrives at your
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site. No set of anti-spam tools will block all spam without blocking some
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portion of legitimate mail as well. Therefore, these FEATUREs are designed
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to prevent as much spam as possible without blocking legitimate mail.
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These tools are discussed in /usr/share/sendmail/cf/README. Read the
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section entitled "ANTI-SPAM CONFIGURATION CONTROL". Example usage and
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additional tools can be found in /usr/share/sendmail/cf/cf/knecht.mc.
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