套件：sendmail、m4(編碼轉換)、sendmail-cf目錄：/etc/mail/
/var/log/mail/
/var/log/maillog
/var/spool/mail
設定檔：/etc/mail/sendmail.mc
拿掉127.0.0.1改為0.0.0.0 執行m4 sendmail.mc > sendmail.cf
收送信埠：MTA 送信 25 port
MUA Mail User Agent (dovecot服務 /etc/dovecot.conf)
POP3 收信 110 port
IMAP 收/送 143 port
POP3s 加密 995 port
IMAPs 加密 993 port
指令發送信件
#mail -s test abc@abc.com
xxxxx 本文
. <-結束
Cc:
EHLO localhost
MAIL FROM: abc@abc.com
RCPT TO: xyz@xyz.com
Relaying denied. IP name lookup failed.
DATA
Subject:hello
. <-離開
※Relay問題? 設定檔 /etc/mail/access 將Relay區放入即可 Ex. 140.137.215 RELAY
makemap -V hash access.db < access
SMTP認證：
#yum -y install cyrus-sasl*
修改 /etc/mail/sendmail.mc 第52,53行,刪除dn1字串
#m4 sendmail.mc > sendmail.cf
#service saslauthd restart
#service sendmail restart
郵件主機名稱：
1.#hostname a234.snpy.org
2./etcsysconfig/network 加入HOSTNAME=a234.snpy.org
3./etc/hosts 加入140.137.215.234 a234.snpy.org
收多網域信件： /etc/mail/local-host-name 加入domain
