telnet smtp

Type telnet 25,and then press ENTER.

Type EHLO , and then press ENTER.

Type AUTH LOGIN. The server responds with an encrypted prompt for your user name.

Enter your user name encrypted in base 64. You can use one of several tools that are available to encode your user name.

The server responds with an encrypted base 64 prompt for your password. Enter your password encrypted in base 64.

Type MAIL FROM:@domain.com>, and then press ENTER. If the sender is not permitted to send mail, the SMTP server returns an error.

Type RCPT TO:@remotedomain.com>,and then press ENTER.If the recipient is not a valid recipient or the server does not accept mail for this domain, the SMTP server returns an error.

Type DATA.

If desired, type message text, press ENTER, type a period (.), and then press ENTER again.

If mail is working properly, you should see a response similar to the following indicating that mail is queued for delivery:

参考: https://technet.microsoft.com/en-us/library/aa995718(v=exchg.65).aspx
###############

Connected to smtp.qq.com.
Escape character is '^]'.
220 **********************************************************
ehlo qq
250-CNSH043634 Hello a [10.10.100.65]
250-SIZE 10485760
250-8BITMIME
250-PIPELINING
250-AUTH LOGIN
250 XXXA
auth login
334 VXNlcm5hbWU6
Y3VpemhpbGlhbmczNDQ= #这位是base64编码后的账号
334 UGFzc3dvcmQ6
Q3psMTEwMTIz #这位是base64编码后的密码
235 Authentication succeeded
MAIL FROM:73xxxxxx@qq.com
250 OK
RCPT TO:xxxx344@qq.com
250 Accepted
DATA
354 Enter message, ending with "." on a line by itself
hehhe
ceshi
.
250 OK id=1bRdmd-0008Qm-Nm
Connection closed by foreign host.
#################

本文出自 “学通信，第一份工作运维” 博客，请务必保留此出处http://cuidehua.blog.51cto.com/5449828/1829789