1. /var/spool/mail/root にメールが届く
2. mail コマンドでメールを確認する
3. 数字＋Enterで任意のメールを読む
4. d数字＋Enterで任意のメールを削除
5. h でメールリストを開く
6. q で閉じる
7. /root/mbox に既読メールが保存される（Saved ** messages in mbox）
8. mail -f で既読メールを確認する

# mail
 U754 MAILER-DAEMON@kd-adm  Mon Oct 15 01:00 251/8692  "Undelivered Mail Returned to Sender"
>U755 MAILER-DAEMON@kd-adm  Mon Oct 15 02:23 251/8692  "Undelivered Mail Returned to Sender"
 U756 MAILER-DAEMON@kd-adm  Mon Oct 15 02:23 246/8417  "Undelivered Mail Returned to Sender"

# 756

# h
 U754 MAILER-DAEMON@kd-adm  Mon Oct 15 01:00 251/8692  "Undelivered Mail Returned to Sender"
 U755 MAILER-DAEMON@kd-adm  Mon Oct 15 02:23 251/8692  "Undelivered Mail Returned to Sender"
> 756 MAILER-DAEMON@kd-adm  Mon Oct 15 02:23 246/8417  "Undelivered Mail Returned to Sender"

# d 750-753

# ll /var/spool/mail/
合計 0
-rw-rw---- 1 istadmin mail 0  8月  2 19:53 2013 root
-rw-rw---- 1 istpika  mail 0  8月  2 19:53 2013 taro

# rm -rf /var/spool/mail/root

1. s：SUBJECT
2. ：TO
3. f：FROM

メール本文入力後、ピリオドで送信

# mail -s "SUBJECT" clown@example.com -- -f FROM@mail.com
mail body
.
EOT

1. s：SUBJECT
2. r：FROM
3. ：TO

メール本文入力後、ピリオドで送信

# mail -s "SUBJECT" -r FROM@mail.com clown@example.com
mail body
.
EOT

# crontab -e

MAILTO=""
*/1 * * * * /usr/local/bin/exec

# vi /etc/crontab

SHELL=/bin/bash
PATH=/sbin:/bin:/usr/sbin:/usr/bin
#MAILTO=root
MAILTO=""
HOME=/

# For details see man 4 crontabs

# Example of job definition:
# .---------------- minute (0 - 59)
# |  .------------- hour (0 - 23)
# |  |  .---------- day of month (1 - 31)
# |  |  |  .------- month (1 - 12) OR jan,feb,mar,apr ...
# |  |  |  |  .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat
# |  |  |  |  |
# *  *  *  *  * user-name command to be executed

# vi /etc/anacrontab

# /etc/anacrontab: configuration file for anacron

# See anacron(8) and anacrontab(5) for details.

SHELL=/bin/sh
PATH=/sbin:/bin:/usr/sbin:/usr/bin
#MAILTO=root
MAILTO=""
# the maximal random delay added to the base delay of the jobs
RANDOM_DELAY=45
# the jobs will be started during the following hours only
START_HOURS_RANGE=3-22

#period in days   delay in minutes   job-identifier   command
1       5       cron.daily              nice run-parts /etc/cron.daily
7       25      cron.weekly             nice run-parts /etc/cron.weekly
@monthly 45     cron.monthly            nice run-parts /etc/cron.monthly

# vi /etc/cron.d/0hourly

SHELL=/bin/bash
PATH=/sbin:/bin:/usr/sbin:/usr/bin
#MAILTO=root
MAILTO=""
HOME=/
01 * * * * root run-parts /etc/cron.hourly

mailコマンドで送信時に次のような警告が出る。

send-mail: warning: inet_protocols: IPv6 support is disabled: Address family not supported by protocol
send-mail: warning: inet_protocols: configuring for IPv4 support only
postdrop: warning: inet_protocols: IPv6 support is disabled: Address family not supported by protocol
postdrop: warning: inet_protocols: configuring for IPv4 support only

プロトコルはIPv4とIPv6が両方とも対応になっているようなので、設定ファイル（/etc/postfix/main.cf）を開き、ipv4 だけにする。

# vi /etc/postfix/main.cf

#inet_protocols = all
inet_protocols = ipv4

デーモン再起動。

# /etc/init.d/postfix restart