Bounce handling simplified

I am a strong believer that bounce handling should be designed to remove addresses that have no human on the other end while not removing addresses that have a real recipient on the other end.
Bounce handling should be designed to appropriately manage your subscriber base. Delivery problems are the consequence if you don’t do that. They shouldn’t be the reason you bounce handle, though.
Context matters.
My experience tells me that senders that think about the impact of their sends can do things that “break the rules” while still being respectful of their subscribers and still see good delivery.

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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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Blocked for phishing

A couple clients recently have had bounces from different places indicating that their mails were caught by the recipients’ anti-virus filter. These are some of my better clients sending out daily newsletters. They’ve been mailing for years and I know that they are not phishing. They asked me to investigate the bounce messages.
The information I had to work with was minimal. One bounce said:

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Reputation

Reputation is the buzzword in delivery these days. Everyone talks about building a good reputation and how to do it. Makes sense, the ISPs are always hammering on reputation and how critical reputation is. The more I talk with delivery folks on the ESP side of thing, the move I realize that there is a fundamental disconnect between what the ESPs mean when they say reputation and what the ISPs mean when they say reputation.
Many people handling delivery think that the bulk of reputation is wrapped up in complaint rates and bounce rates. I think they know the ISPs measure more than just complaints and bounces (spamtraps!) but really believe that most of developing a good reputation is all about keeping those complaints low.
This perspective may have been true in the past, but is becoming less true as time goes on. There are a lot of very smart people managing incoming mail at the ISPs and they are constantly looking for ways to better meet the desires of their customers. Lest we forget, their customers are not the senders, their customers are the end users. Their customers are not senders.
Part of meeting the needs of end users means actually giving them a way to provide feedback. AOL started the trend with the this-is-spam button, and other ISPs (ones that controlled the user interface at least) followed suit. For a very long time, reputation was dominated by complaint percentages, with modifiers for number of spamtrap addresses and number of non-existent users.
The problem is, these numbers were easy to game. Spammers could modify their metrics such that their email would end up in the inbox. In response, the ISPs started measuring things other than complaints, bounces and spamtraps. These other measurements are strong modifiers to complaints, such that mailers with what used to be acceptable complaint rates are seeing their mail end up bulked or even rejected.
Recently, AOL seems to have made some subtle modifications to their reputation scores. The result is mailers who have previously acceptable complaint rates are seeing delivery problems. When asked, AOL is only saying that it is a reputation issue. Lots of senders are trying to figure out what it is that is more important than complaints.
Tomorrow, I will talk about what I think AOL could be measuring.

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