部分服务器不支持此操作
Step1.
User@DESKTOP:~$ host -t mx yeah.net
yeah.net mail is handled by 10 yeahmx01.mxmail.netease.com.
yeah.net mail is handled by 50 yeahmx00.mxmail.netease.com.
Step2.任选一个服务器
User@DESKTOP:~$ telnet yeahmx01.mxmail.netease.com 25
Trying 123.58.177.214...
Connected to yeahmx01.mxmail.netease.com.
Escape character is '^]'.
220 yeah.net Anti-spam GT for Coremail System (yeah[20141016])
ehlo smtp.test.com
250-mail
250-PIPELINING
250-AUTH LOGIN PLAIN
250-AUTH=LOGIN PLAIN
250-coremail 1Uxr2xKj7kG0xkI17xGrU7I0s8FY2U3Uj8Cz28x1UUUUU7Ic2I0Y2UFvTwD0UCa0xDrUUUUj
250-STARTTLS
250-SIZE 73400320
250-SMTPUTF8
250 8BITMIME
MAIL FROM:<test@test.com>
250 Mail OK
RCPT TO:<right@yeah.net>
250 Mail OK
RCPT TO:<wrong@yeah.net>
550 User not found: wrong@yeah.net
Connection closed by foreign host.