In the email delivery space there are a lot of numbers we talk about including bounce rates, complaint rates, acceptance rates and inbox delivery rates. These are all good numbers to tell us about a particular campaign or mailing list. Usually these metrics all track together. Low bounce rates and low complaint rates correlate with high delivery rates and high inbox placement. But sometimes the...
There are a number of folks who tell me there can be no zombie addresses on their lists, they aggressively remove any address that bounces. The problem is that zombie addresses don’t bounce, at least not always. And even when ISPs say they have a policy to bounce email after a certain period of time with no access, that’s not always put into practice. How do I know that ISPs...
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...
I often get clients and potential clients asking me to tell them what the absolute best ESP is. “You’re an expert in the field, which ESP will give me the best inbox delivery?” The thing is, there isn’t an answer to that question. ESPs have expertise in sending large amounts of mail. All have staff that manage and monitor MTAs. Most have staff that provide advice on...
James from Cloudmark has his own insight on spamtraps.
Over the weekend, one of the major ISPs purged a lot of abandoned accounts from their system. This has resulted in a massive increase in 550 user unknown bounces at that ISP. This ISP is one of those that uses bounces to feed into their reputation system and the purge may cause otherwise good senders to be blocked temporarily. Talking to clients and other industry folks, it looks like the...
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...
Return Path released their global delivery report for the second half of 2009. To put together the report, they look at mail delivery to the Mailbox Monitor accounts at 131 different ISPs for 600,000+ sends. In the US, 20% of the email sent by Mailbox Monitor customers to Return Path seed accounts doesn’t make it to the inbox. In fact, 16% of the email just disappears. I’ve blogged in...
A number of people are reporting seeing a new bounce from Yahoo. “smtp;553 Mail from x.x.x.x not allowed – [10]”. My clients have been asking and other people have been asking about this. It seems that something is changing at Y! More information as I hear it.
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