sendmail 튜닝

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1. 기본 설정값 조정
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- Load Average가 100 이 넘으면 Queue 에 메일을 넣는다.
O QueueLA=100

- Load Average가 128 이 넘으면 메일 수신 접속을 거부 한다.
O RefuseLA=128

- 자식 프로세스 생성 최대 값, 이 수치 이상으로 프로세스가 생성 되면 접속을 거부한다.
O MaxDaemonChildren=64

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2. sendmail 수신 / 발신 전용 프로세스 분리
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- /etc/mail 에 sendmail_recv.cf, sendmail_queue.cf 설정

- sendmail_recv.cf ( Defer Mode )

#d defer delvery attempts (don't deliver)
O DeliveryMode=d

# location of pid file
O PidFile=/var/run/sendmail_recv.pid

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Delivery Mode
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There are a number of delivery modes that sendmail can operate in, set by the DeliveryMode ( d) configuration option. These modes specify how quickly mail will be delivered. Legal modes are:

i deliver interactively (synchronously)
b deliver in background (asynchronously)
q queue only (don't deliver)
d defer delvery attempts (don't deliver)

There are tradeoffs. Mode i gives the sender the quickest feedback, but may slow down some mailers and is hardly ever necessary. Mode b delivers promptly but can cause large numbers of processes if you have a mailer that takes a long time to deliver a message. Mode q minimizes the load on your machine, but means that delivery may be delayed for up to the queue interval. Mode d is identical to mode q except that it also prevents all the early map lookups from working; it is intended for ``dial on demand'' sites where DNS lookups might cost real money. Some simple error messages (e.g., host unknown during the SMTP protocol) will be delayed using this mode. Mode b is the usual default.
If you run in mode q (queue only), d (defer), or b (deliver in background) sendmail will not expand aliases and follow .forward files upon initial receipt of the mail. This speeds up the response to RCPT commands. Mode i cannot be used by the SMTP server.
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- sendmail_queue.cf ( Background Mode )

# location of pid file
O PidFile=/var/run/sendmail_queue.pid

# default delivery mode
O DeliveryMode=b

- /etc/init.d/sendmail

start() {
    # Start daemons.

    ###########################################################################
    # receiving daemon ( defer mode )
    ###########################################################################
    echo -n $"Starting $prog: sendmail_recv "
    if test -x /usr/bin/make -a -f /etc/mail/Makefile ; then
      make all -C /etc/mail -s > /dev/null
    else
      for i in virtusertable access domaintable mailertable ; do
        if [ -f /etc/mail/$i ] ; then
            makemap hash /etc/mail/$i < /etc/mail/$i
        fi
      done
    fi
    /usr/bin/newaliases > /dev/null 2>&1

    daemon --check sendmail_recv /usr/sbin/sendmail -L sendmail_recv -bd -C/etc/mail/sendmail_recv.cf
    RETVAL=$?
    echo
    [ $RETVAL -eq 0 ] && touch /var/lock/subsys/sendmail

    ###########################################################################
    # process queue daemon
    ###########################################################################
    if ! test -f /var/run/sendmail_queue.pid ; then
        echo -n $"Starting $prog: sendmail_queue "
        touch /var/run/sendmail_queue.pid
        chown smmsp:smmsp /var/run/sendmail_queue.pid
        if [ -x /usr/bin/selinuxenabled ] && /usr/bin/selinuxenabled; then
            /sbin/restorecon /var/run/sendmail_queue.pid
        fi

        daemon --check sendmail_queue /usr/sbin/sendmail -L sendmail_queue -C/etc/mail/sendmail_queue.cf -q1m
        RETVAL=$?
        echo
        [ $RETVAL -eq 0 ] && touch /var/lock/subsys/sendmail_queue
    fi

    return $RETVAL
}

stop() {
    # Stop daemons.
    echo -n $"Shutting down $prog: "
    killproc sendmail
    RETVAL=$?
    echo
    [ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/sendmail
  [ $RETVAL -eq 0 ] && rm -f /var/run/sendmail_queue.pid
  [ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/sendmail_queue
    return $RETVAL
}
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