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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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A brief guide to spamtraps

“I thought spamtraps were addresses harvested off webpages.”

“I thought spamtraps were addresses that were valid and now aren’t.”

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The sledgehammer of confirmed opt-in

We focused Monday on Trend/MAPS blocking fully confirmed opt-in (COI) mail, because that is the Gold Standard for opt-in. It is also Trend/MAPS stated policy that all mail should be COI. There are some problems with this approach. The biggest is that Trend/MAPS is confirming some of the email they receive and then listing COI senders.
The other problem is that typos happen by real people signing up for mail they want. Because MAPS is using typo domains to drive listings, they’re going to see a lot of mail from companies that are doing single opt-in. I realize that there are problems with single opt-in mail, but the problems depends on a lot of factors. Not all single opt-in lists are full of traps and spam and bad data.
In fact, one ESP has a customer with a list of more than 50 million single opt-in email addresses. This sender mails extremely heavily, and yet sees little to no blocking by public or private blocklists.
Trend/MAPS policy is singling out senders that are sending mail people signed up to receive. We know for sure that hard core spammers spend a lot of time and money to identify spamtraps. The typo traps that Trend/MAPS use are pretty easy to find and I have no doubt that the real, problematic spammers are pulling traps out of their lists. Legitimate senders, particularly the ESPs, aren’t going to do that. As one ESP rep commented on yesterday’s post:

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