Yahoo delays, part 3: Yahoo speaks

Yahoo is aware of the recent problems and have been working feverishly to fix them. A Yahoo employee posted to a mailing list earlier today, explaining some of the recent issues. The summary is:
1) The Yahoo delays are a result of a tighter spam filtering policy. The delays are the result of the system erroneously recognizing email as spam and deferring delivery. They do believe that retrying long enough will result in all mail being delivered to Yahoo recipients.
2) They have been continually making fixes to the system over the last few days and senders should see queues start to empty over the next few hours.
3) They believe the adjustments made will resolve the deferral problems. If you continue to see problems, you can contact them through the form at http://postmaster.yahoo.com/.
4) They are working to provide more self-serve information at http://postmaster.yahoo.com/ as well as timely service updates.
Loose ends from my previous Yahoo posts:

  1. The rumors of an attack were just that, rumors.
  2. The Yahoo blog post about outbound servers is unrelated to the problems seen by senders recently. Outbound SMTP servers are not the same as the MX machines.

Good news all around. Thanks to the people at Yahoo for working so diligently to fix the problems.

Yahoo delays, part 2
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There is one major change that deserves its own discussion. Yahoo is now using the SBL, XBL and PBL to block connections from listed IP addresses. These are public blocklists run by Spamhaus. Each of them targets a different type of spam source.
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Additionally, the SBL will list spam gangs and spam supporters. Spam supporters include networks that provide services to spammers and do not take prompt action to remove the spammers from their services.
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I have forwarded those logs onto Yahoo who are looking into the issue. I have also talked with one of the Spamhaus volunteers and Spamhaus is aware of the issue as well.
The right people are looking at the issue and Spamhaus and Yahoo are both working on fixing this.
Thanks for the reports and for the logs.

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Deeply held beliefs by many senders aside, Yahoo is not greylisting. Yahoo is using temporary failures (4xx) as a way to defer and control mail coming into their servers and their users.
I think much of the problem is that the definition of greylisting is not well understood by the people using the term. Greylisting generally refers to a process of refusing email with a 4xx response the first time delivery is attempted and accepting the email at the second delivery attempt. There are a number of ways to greylist, per message, per IP or per from address. The defining feature of greylisting is that the receiving MTA keeps track of the messages (IP or addresss) that it has rejected and allows the mail through the second time the mail is sent.
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