RE: Validating email addresses

here is an actual conversation with midrange.com's mail server:

220 linux.midrange.com; ESMTP Thu, 25 Apr 2002 17:48:26 -0500
help
502 5.3.0 Sendmail 8.11.6 -- HELP not implemented
HELO
250 linux.midrange.com Hello [63.165.169.127], pleased to meet you
MAIL FROM:CHRIS.BIPES@CROSS-CHECK.COM
250 2.1.0 CHRIS.BIPES@CROSS-CHECK.COM... Sender ok
RCPT TO:DAVID
250 2.1.5 DAVID... Recipient ok

I used NSLOOKUP for an MX record to midrange.com and received three entries:

set type=mx
>
midrange.com
Nonauthoritative answer:
midrange.com    preference = 10, mail exchanger = linux.midrange.com
midrange.com    preference = 20, mail exchanger = circuit1.midrange.com
midrange.com    preference = 30, mail exchanger = circuit2.midrange.com

Authoritative answers can be found from:
linux.midrange.com      internet address = XXX.XXX.XXX.XXX
circuit1.midrange.com   internet address = XXX.XXX.XXX.XXX
circuit2.midrange.com   internet address = XXX.XXX.XXX.XXX

This is done interactively.  Hackers or e-mail pirates script this and
create data bases.

Sorry for picking on you David.  Hope you don't mind.   By the way this was
all gathered from AS400 5250 terminal using the command nslookup and telnet.

Christopher K. Bipes      mailto:ChrisB@Cross-Check.com
Operations & Network Mgr  mailto:Chris_Bipes@Yahoo.com
CrossCheck, Inc.          http://www.cross-check.com
6119 State Farm Drive     Phone: 707 586-0551 x 1102
Rohnert Park CA  94928    Fax: 707 586-1884


-----Original Message-----
From: John Ross [mailto:jross-ml@netshare400.com]
Sent: Thursday, April 25, 2002 3:47 PM
To: midrange-l@midrange.com
Subject: Re: Validating email addresses


I am not sure you understand the purpose of the MX record. It is for mail,
it tells which server(s) is handling the email. When I say domain  I should
of said web server (WWW). If you ping midrange.com it will check the AS400.
If you ping linux.midrange.com it will check the first mail server. But you
have no idea from david@midrange.com to ping linux.midrange.com, without
looking up the MX record.