20% of email doesn't make it to the inbox

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 the past about previous Return Path deliverability studies. The recommendations and comments in those previous posts still apply. Senders must pay attention to engagement, permission, complaints and other policy issues. But none of those things really explain why email is missing.
Why is so much mail disappearing? It doesn’t match with the philosophy of the ISPs. Most ISPs do their best to deliver email that they accept and I don’t really expect that ISPs are starting to hard block so many Return Path customers in the middle of a send. The real clue came looking at the Yahoo numbers. Yahoo is one of those ISPs that does not delete mail they have accepted, but does slow down senders. Other ISPs are following Yahoo’s lead and using temporary failures as a way to regulate and limit email sent by senders with poor to inadequate reputations. They aren’t blocking the senders outright, but they are issuing lots of 4xx “come back later” messages.
What is supposed to happen when an ISP issues a 4xx message during the SMTP transaction is that email should be queued and retried. Modern bulk MTAs (MessageSystems, Port25, Strongmail) allow senders to fine tune bounce handling, and designate how many times an email is retried, even allowing no retries on a temporary failure.
What if the missing mail is a result of senders aggressively handling 4xx messages? Some of the companies I’ve consulted for delete email addresses from mailing lists after 2 or 3 4xx responses. Other companies only retry for 12 – 24 hours and then the email is treated as hard bounced.
Return Path is reporting this as a delivery failure, and the tone of discussion I’m seeing seems to be blaming ISPs for overly aggressive spamfiltering. I don’t really think it’s entirely an ISP problem, though. I think it is indicative of poor practices on the part of senders. Not just the obvious permission and engagement issues that many senders deal with, but also poor policy on handling bounces. Perhaps the policy is fine, but the implementation doesn’t reflect the stated policy. Maybe they’re relying on defaults from their MTA vendor.
In any case, this is yet another example of how senders are in control of their delivery problems. Better bounce handling for temporary failures would lower the amount of email that never makes it to the ISP. This isn’t sufficient for 100% inbox placement, but if the email is never handed off to the ISP it is impossible for that email to make it to the inbox.

Related Posts

The delivery communication gap

There seems to be a general uptick in the number of specific questions that ESPs and commercial senders are asking recently. I’m getting them from clients, and I’m hearing similar stories from my various contacts over on the ISP side. The questions cover a wide range of areas in email delivery, but the underlying issue is really that there are no real fixed rules about email delivery anymore. The only rule is “send mail users want to receive” and there are no specific guidelines to how to do that.
This is frustrating for a lot of people. They want to know exactly how many complaints they need to stay under. They want to know what “engagement” means and how exactly the ISPs are measuring it. They want to know all of the metrics they need to meet in order to get mail to the inbox.
There is a lot of frustration among senders because they’re not getting the answers they think they need and they feel like the ISPs aren’t listening to them.
Likewise there is a lot of frustration among ISPs because they’re giving answers but they feel like they’re not being heard.
Some of the problem is truly a language difference. A lot of delivery people on the ESP side are marketers first and technologists second. They don’t have operational experience. They don’t have that any feel for the technology behind email and can’t map different failure modes onto their causes. Some of them don’t have any idea how email works under the covers. Likewise, a lot of postmaster people are technologists. They deeply understand their customers and their email servers and don’t speak marketing.
The other issue is the necessary secrecy. Postmasters have been burned in the past and so they have to be vague about what variables they are measuring and how they are weighting them.
All of this leads to a very adversarial environment.
I’ve been talking with a lot of people about this and none of us have any real answers to the solution. Senders say the ISPs should spend more time explaining to the senders what they need to do. ISPs say the senders should stop sending spam.
Am I quite off base here? Is there no communication gap? Am I just cynical and missing some obvious solution? Anyone have any suggestions on how to solve the issue?

Read More

Delivery case study

Mailchimp published a case study looking at a customer moving from sending in house to using Mailchimp.

Read More

Rescuing reputation

One of the more challenging things I do is work with companies who have poor reputations that they’re trying to repair. These companies have been getting by with poor practices for a while, but finally the daily delivery falls below their pain threshold and they decide they need to fix things.
That’s when they call me in, usually asking me if I can go to the ISPs and tell the ISPs that they’re not spammers, they’re doing everything right and will the ISP please stop unfairly blocking them. Usually I will agree to talk to the ISPs, if fixing the underlying problems doesn’t improve their delivery on its own. But before we can talk to the ISPs, we have to try to fix things and at least have some visible changes in behavior to take to them. Once they have externally visible changes, then we can ask the ISPs for a little slack.
With these clients there isn’t just one thing they’ve done to create their bad reputation. Often nothing they’re doing is really evil, it’s just a combination of sorta-bad practices that makes their overall reputation really bad. The struggle is fixing the reputation requires more than one change and no single change is going to necessarily make an immediate improvement on their reputation.
This is a struggle for the customer, because they have to start thinking about email differently. Things have to be done differently from how they’ve always been done. This is a struggle for me because I can’t guarantee if they do this one thing that it will have improved delivery. I can’t guarantee that any one thing will fix their delivery, because ISPs measure and weight dozens of things as part of their delivery making decisions. But what I can guarantee is that if they make the small improvements I recommend then their overall reputation and delivery will improve.
What small improvement have you made today?

Read More