smtp - 如何检查我的 ISP 是否阻止了端口 25？

Question

我应该如何检查我的 ISP 是否阻止了端口 25？

Answer 1

cmd> telnet <some well known email provider IP> 25

确定哪个主机(子域)正在监听端口 25:

nslookup -q=MX <top-level domain>

例如:

cmd> nslookup -q=MX gmail.com

gmail.com       MX preference = 50, mail exchanger = gsmtp147.google.com
gmail.com       MX preference = 50, mail exchanger = gsmtp183.google.com
gmail.com       MX preference = 5, mail exchanger = gmail-smtp-in.l.google.com
gmail.com       MX preference = 10, mail exchanger = alt1.gmail-smtp-in.l.google.com
gmail.com       MX preference = 10, mail exchanger = alt2.gmail-smtp-in.l.google.com

gsmtp147.google.com     internet address = 209.85.147.27
gsmtp183.google.com     internet address = 64.233.183.27
gmail-smtp-in.l.google.com      internet address = 64.233.183.114

cmd> telnet gsmtp147.google.com 25

220 mx.google.com ESMTP l27si12759488waf.25

在 Linux 上，你可以“挖掘”，我猜。