メールの存在確認

##メールの存在確認
> nslookup
> set type=mx
> example.com
Server: *******
Address: ***.***.*.*
example.com MX preference = 10,mail exchanger = mail.example.com
example.com nameserver = ns.example.com
mail.example.com internet address = ww.xx.yy.zz
ns.example.com internet address = ***.***.**.**


> telnet
Microsoft (R) Windows 2000 (TM) Version 5.00 (Build 2195)
Microsoft Telnet クライアントへようこそ Telnet Client Build 5.00.99201.1
エスケープ文字は 'CTRL+]' です
Microsoft Telnet> open mail.example.com 25
接続中: mail.example.com...

220 SMTP Server service ready;
helo my.example.com
250 mail.example.com
mail from: <>
250 OK
rcpt to: <joe@example.com>
250 OK
rcpt to: <bogus_sow5nt2df@example.com>
550 Mailbox unavailable <sow5nt2df@example.com>
quit
221 closing transmission channel