[arin-ppml] How bad is it really?

Stephen Sprunk stephen at sprunk.org
Sat Jul 17 23:22:51 EDT 2010

On 13 Jul 2010 01:48, Ted Mittelstaedt wrote:
> Before getting too worked up, please keep in mind that the fact that
> the mail message was ACCEPTED by your mail system and not immediately
> bounced, indicates that there's a valid e-mail box there.

No, it does not.  I'm aware of at least one firewall appliance that
"accepts" all mail submitted to any address and, after doing some
security checks, blindly forwards it to an internal smarthost (which
might or might not send a DSN if the address is invalid).  I'm not sure
whether this is an RFC violation, but either way it's existence proof
that the SMTP response code that ARIN receives is _not_ a reliable
indication that the address used does in fact correspond to an actual

And, of course, we all know about mailboxes that reside at /dev/null,
spam filtering systems, old mailboxes for ex-employees, etc. that mean
some (unknown) fraction of mail never gets seen by a human even if the
address _does_ have a valid mailbox of some sort, so validity in that
sense is a meaningless measure anyway.

> I'd hazard a guess that if you didn't click on the link at all that
> ARIN is going to still consider the POC  "most likely valid".

Why would they?  They sent an email and the intended recipient didn't
click one of the links.  Either the message never reached the recipient
or the recipient disregarded it, which indicates that email address is
not a reliable means of contacting them--and that's what we're trying to
determine, isn't it?


Stephen Sprunk         "God does not play dice."  --Albert Einstein
CCIE #3723         "God is an inveterate gambler, and He throws the
K5SSS        dice at every possible opportunity." --Stephen Hawking

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