ciscopix防火墙接管smtp

   现象：
   telnet
   mail.aaaaaaaaaaaaaa.com 25
   Trying ddd.ddd.ddd.ddd…
   Connected to mail.aaaaaaaaaaaaaa.com.
   Escape character is ‘^]‘.
   220 ****0**********************************
   ehlo aaaaaaaaaaaaaa.com
   502 Error: command not implemented
   helo aaaaaaaaaaaaaa.com
   250 mail01.aaaaaaaaaaaaaa.com
   ehlo aaaaaaaaaaaaaa.com
   502 Error: command not implemented
   连接后出现
   220 ****0**********************************
   并且不支持ESMTP
   解决办法：
   no fixup protocol smtp 25
   If you‘re getting the *** banner, and EHLO not recognised and you have a PIX
   in the way, it‘s fixup, and there‘s nothing else you can do. To give ammo if
   you need it, Cisco deprecated fixup in v7 of the PIX OS, due to it not
   understanding anything beyond RFC 821.
   From their own docs:
   The fixup protocol smtp command enables the Mail Guard feature. This restricts
   mail servers to receiving the seven minimal commands defined in RFC 821,
   section 4.5.1 （HELO, MAIL, RCPT, DATA, RSET, NOOP, and QUIT）。 All other
   commands are rejected.
   Microsoft Exchange server does not strictly comply with RFC 821 section 4.5.1,
   using extended SMTP commands such as EHLO. PIX Firewall will convert any such
   commands into NOOP commands, which as specified by the RFC, forces SMTP
   servers to fall back to using minimal SMTP commands only. This may cause
   Microsoft Outlook clients and Exchange servers to function unpredictably when
   their connection passes through PIX Firewall.