AOL transmitting 4xx error for user unknown

AOL is currently returning “451 4.3.0 <invaliduser@aol.com>: Temporary lookup failure” in some cases when they really mean “550 user unknown.” This message from AOL should be treated as 5xx failure and the message should not be retried (if at all possible) and the failure should be counted as a hard bounce for list management purposes.
This is something broken at AOL’s end, and the guys with the magic fingers that keep the system running are working to fix it. Right now there doesn’t seem to be an ETA on a fix, though.
Even if you are a sender who is able to stop the retries, you may see some congestion and delays when sending to AOL for the time being. Senders who don’t get the message, or who are unable to stop their MTAs from retrying 4xx mail will continue to attempt delivery of these messages until their servers time out. This may cause congestion for everyone and a noticeable  slowdown on the AOL MTAs.
AOL blog post on the issue
HT: Annalivia

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AOL EWL: low complaints no longer enough

This morning AOL announced some changes to their Enhanced White List. Given I’ve not talked very much about the AOL EWL in the past, this is as good a time as any to talk about it.
The AOL Enhanced Whitelist is for those senders that have very good practices. Senders on the EWL not only get their mail delivered to the inbox, but also have links and images enabled by default. Placement on the EWL is done solely on the basis of mail performance and only the best senders get on the list.
The new announcement this morning says that AOL will take more into account than just complaints. Previously, senders with the lowest complaint rates qualified for the EWL. Now, senders must also have a good reputation in addition to the low complaint rates. Good reputation is a measure of user engagement with a particular sender.
This change only reinforces what I and many other delivery experts have been saying: The secret to good delivery is to send mail recipients want. ISPs are making delivery decisions based on those measurements. Send mail that recipients want, and there are few delivery problems.
For a long time good delivery was tied closely to complaint rates, so senders focused on complaints. Spammers focused on complaints too, thus managing to actually get some of their spam delivered. ISPs noticed and started looking at other ways to distinguish wanted mail from spam. One of the better ways to separate spam from wanted mail is to look at user engagement. And the ISPs are measuring engagement and using that measurement as part of their decision making process. Send so much mail users don’t read it, and your reputation goes down followed by your delivery rates.

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Soft bounces and rate limiting

What is your policy for handling soft bounces? What do you consider a soft bounce? What is the right thing to do about soft bounces?
The first step in talking about soft bounces is to define them. When I talk about soft bounces, I mean mail that has been rejected with a 4xx response during the SMTP transaction. As described by RFC5321, when a recipient MTA responds with a 4xx it is telling the sending MTA “Wait! I can’t take this mail right now. Come back a little later and try again.” The sending MTA will then continue to attempt to deliver the message until either it is delivered or until it hits the max delivery time, usually 3 – 5 days.
In a well behaved and RFC compliant MTA, messages that have reached the maximum time without delivery due to 4xx rejections will be converted to permanent rejections (5xx). With a correct MTA, this means too many emails in a row timing out shoud result in an email address being removed from future mailings.
For a number of reasons some ISPs, notably Yahoo, are using 4xx responses to slow down mail from some senders. Many senders treat this as a inconvenience and a frustration and try to figure out how to get around the rate limiting. The UK DMA published an article on soft bounces with the following words of wisdom.

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Links for 1/15/10

A lot has happened this week.
Spammers and scammers are attempting to steal money from people attempting to donate money to those in earthquake devastated Haiti. A number of places, including CNN and CAUCE, are warning people who want to donate online to do so through trustworthy links. Don’t click on links in unsolicited emails nor on random websites.
AOL laid off most of their postmaster team. This is going to have a significant impact on sender support provided by AOL. The background chatter I’m hearing indicates that there is likely to be response delays of days to weeks for support tickets.
Pivotal Veracity was acquired by Unica, a marketing software company. Industry buzz says that PV will be run as a subsidiary and maintain their independent customer base.
Spamhaus launched a new website, which includes a link for a domain based URI blocklist. There’s not much information available about this new blocklist, but it’s likely to function similar to SURBL and URIBL.
The lethic botnet was penetrated and disabled. Dark Market, one of the large credit card number trading sites, was taken down and the proprietor arrested.

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