注意：本文僅供實驗學習，請勿故意發送垃圾騷擾郵件。
以QQ郵箱為例
- 查詢郵件服務器地址
> nslookup -qt=MX qq.com
qq.com MX preference = 10, mail exchanger = mx3.qq.com
qq.com MX preference = 20, mail exchanger = mx2.qq.com
qq.com MX preference = 30, mail exchanger = mx1.qq.com
qq.com nameserver = ns3.qq.com
qq.com nameserver = ns4.qq.com
qq.com nameserver = ns2.qq.com
qq.com nameserver = ns1.qq.com
ns1.qq.com internet address = 101.89.19.165
ns1.qq.com internet address = 157.255.246.101
ns1.qq.com internet address = 183.36.112.46
ns1.qq.com internet address = 203.205.220.251
ns1.qq.com AAAA IPv6 address = 2402:4e00:8030::115
ns2.qq.com internet address = 123.151.66.78
ns2.qq.com internet address = 203.205.249.143
ns2.qq.com internet address = 121.51.160.100
ns2.qq.com AAAA IPv6 address = 2402:4e00:8010:1::11c
ns3.qq.com internet address = 203.205.195.94
ns3.qq.com internet address = 112.60.1.69
ns3.qq.com internet address = 183.192.164.81
ns4.qq.com internet address = 125.39.46.125
ns4.qq.com internet address = 203.205.195.104
ns4.qq.com internet address = 203.205.221.79
ns4.qq.com internet address = 58.144.154.100
ns4.qq.com internet address = 59.36.132.142
- telnet連接郵件服務器發送郵件
telnet mx1.qq.com 25
連接成功后會收到qq郵箱的歡迎信息
220 newxmmxszb63.qq.com MX QQ Mail Server.
EHLO test.tset #隨便寫個，你的歡迎信息
250-newxmmxszb63.qq.com
250-STARTTLS
250-SIZE 73400320
250 OK
MAIL FROM:<admin@test.test> # 發件人
250 OK.
RCPT TO:<yourqq@qq.com> # 收件人
250 OK 1
DATA # 接下來是數據
354 End data with <CR><LF>.<CR><LF>.
from: admin@test.test # 發件人信息（不寫容易被判定為垃圾郵件）
to: yourqq@qq.com # 收件人
subject: Test # 主題
Hello, I am a test email. # 正文 用一個換行+一個點+一個換行來結束
.
250 OK: queued as. # 已經發送
發送后可能會進入垃圾箱。
如果對方有SPF機制，那么就無法偽裝發送。