I am about to submit the following item as a news item, and I would really appreciate if any email admins out there could verify the problem. The text is as follows:
Verizon customers may have noticed a sharp decline in the amount of spam – as well as valid email – that is getting through to them since around February 7th. The problem appears to be the result of a poorly implemented spam-filtering solution called “gray-listing”. As opposed to “black-listing”, which blocks emails from known spammers, “gray-listing” software simply tells the sender, “I’m busy right now, please try again later.”
Most legitimate email servers will wait a minute or so and try to send email again. On the second attempt, the gray-listing software will accept the incoming email. The solution works on spam because spam servers will typically only attempt to send an email once.
But while the solution is very effective on spam, if improperly configured, it can also eliminate most legitimate emails. The gray-listing server must actually receive the email attempt twice. But there is more than one email server there is a chance that the email attempt will be received by a different server. If the two servers don?t communicate gray-list information, the second server will also give a ?busy? response.
Verizon appears to have at least 27 email servers, and no shared gray-list information between them. The chances of any email attempt going to the same server twice are extremely slim, and there is even a chance that the email will bounce 27 times before being allowed. Businesses and consumers have begun to notice that email sent to Verizon customers often never reach their destination because most email servers will not try to send an email more than a few times.
Several attempts have been made to reach Verizon administrators to inform them of the problem, but they are unresponsive, other than to verify that the sender is not black-listed.
Technical Details:
Email administrators may look for the following Verizon server response in relation to this problem:
?550 You are not allowed to send mail:sv9pub.verizon.net
450 Requested mail action not taken-Try later:sv9pub.verizon.net
quit
221 sv9pub.verizon.net closing connection?
