Re: E-Mail Adresses

• Date: Sun, 21 Jan 1996 20:32:43 PST
• From:
  Jay Carlson <nop@nop.com>
• cc: MOO Cows <moo-cows@parc.xerox.com>
• In-reply-to: Your message of "Sun, 21 Jan 96 17:50:34 PST." <Pine.SUN.3.91.960121204836.9020A-100000@lance>

> would it be possible to 'check-out' a given E-MAIL address to see if it 
> actually exists.  Like if passed "david@castle.net" it returns 1, but if 
> I passed it "asfk@castle.net" it would return 0.

In general, no.  

First try: 

smtp = 25;
con = open_network_connection("nop.com", 25);
this:skip_blather(con);
notify(con, "VRFY nop@nop.com");
if (this:response_code(con) = "250")
  return 1;
endif

This doesn't work.  nop.com could very well have a DNS MX record
indicating that all of its incoming mail should be handled by some
other host. (In fact, it does.)

Second try:

con = open_network_connection(this:lookup_mx_record("nop.com"), 25);
this:skip_blather();  notify(con, "VRFY nop@nop.com");
return this:response_code(con) == "250";

Still doesn't work.  There are many compliant SMTP hosts that claim
that all addresses are valid in response to VRFY requests; you'll find
out that i_dont_exist@mitre.org responds positively to a VRFY because
the machine handling mail for MITRE cannot immediately determine this.

In fact, the only technique useful is to send email with a secret to
the address and see if some human then has a copy of the secret.  See
JHM-style autoregistration.

> Also, is IDENT possible on the MOO(Instead of just knowing the host one 
> connects to the MOO with, it also knows the login name of the user).

A number of people have implemented support for the IDENT protocol,
but it won't necessarily give you what you want.  To start with,
IDENT's RFC sez that it should not be used for authentication uses,
and it certainly shouldn't be used so except in tightly controlled
environments, so be careful.

IDENT is intended for informational uses, and it doesn't necessarily
hand back usernames; several well-known internet sites hand back
sequence numbers or encrypted identity information, and a few just
return a constant string for all users.

Jay Carlson
nop@nop.com    nop@kagoona.mitre.org

Flat text is just *never* what you want.   ---stephen p spackman

• E-Mail Adresses
• From: David Matovich <david@castle.net>

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