>>Something not funny has begun happening to emails I send to friends with
>>Yahoo email addresses.
>>
>>During the past few weeks I've had the Mailer Demon at my ISP inform me
>>that Yahoo had refused to accept an email I sent to someone with an
>>"@[EMAIL PROTECTED]
" address, and issued an "error 421".
>>
>>That message further says my ISP isn't going to automatically try and
>>send that email from me again.
>>
>>The message refers me to this Yahoo page:
>>
>>http://help.yahoo.com/l/us/yahoo/mail/postmaster/postmaster-22.html
Sounds to me that they're doing what's called "greylisting"
as an anti spam measure.
How it works:
The mail server at the receiving ISP tells the sending server
"sorry, we're busy now. Please try again later".
Legitimate ISP mail servers will see this msg and will, indeed,
try sending again in a few minutes, typically 15 or so.
The receiving server sees this second msg, matches the
headers and other info to the one from 15 mintues earlier,
and lets it through.
The concept behind this is that a hefty majority of spam
is sent from compromised machines that will just go through
their list of 50,000 recipients, but can't be bothered
to do a second attempt.
Many ISPs are instituting greylisting on, for want
of a better term, questionable incoming e-mail. They'd
whitelist e-mail coming from, for example, ebay.com
and chasemanhattanbank.com, but stuff coming from
mumblefritz123.com would get the delay tactic.
The problem you're facing is that your ISP's mail
server isn't resending 15 minutes later like it,
and other well behaved systems, are supposed to.
Think back to that scene between Lt. Uhura and
Checkhov in "Mirror Mirror". She tells him to
get lost but he doesn't return. He's _supposed_
to return...
ah, wiki wrtieup good it has:
http://en.wikipedia.org/wiki/Greylisting
or... I could be wrong.
--
_____________________________________________________
Knowledge may be power, but communications is the key
dannyb@[EMAIL PROTECTED]
[to foil spammers, my address has been double rot-13 encoded]
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