Share your average bounce rates

The question came up on slack this morning about bounce rate benchmarks. What are the normal / average bounces that different ESPs see? Does region matter? What’s acceptable for bounce rates?

Bounce rate is an overall measure of address quality

Here’s your the chance for ESPs share the data from your customers. We’re interested in anything you care to share. But more detail is always helpful. Some suggestions:

  • Overall bounce rate for 2018.
  • Bounce rate for 2018 compared to 2017.
  • Rate by month.
  • Rate by region (US, EMEA, AsiaPac, etc).
  • Rate by industry.
  • Bounce rates that make you sit up and take notice.

Feel free to add any other numbers. This is just an informal poll of readers.

Anonymization / Privacy note for this post: Generally I don’t approve comments from clearly forged or fake email addresses. If you want your comment to stay anonymous, use an address that’s not been previously approved and it will go into moderation. Please let me know who you are in the text and I will edit before approving the post.

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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.

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Relaying Denied

I’ve got multiple clients right now looking for insights about bounce handling. This means I’m doing a lot of thought work about bounces and what they mean and how they match up and how different ISPs manage delivery and how different ESPs manage delivery and how it all fits together. One thing I’ve been trying to do is contextualize bounces based on what the reason is.
Despite what people may thing, spam filtering isn’t the only reason an email fails to deliver. There are lots of other reasons, too. There is a whole category of network problems like routing issues, TCP failures, DNS failures and such. There are address issues where a recipient simply doesn’t exist, or is blocking a particular sender. There are spam and authentication issues. The discussion of all these issues is way longer than a blog post, and I’m working on that.
One of the interesting bounces that is so rare most people, including me, never talk about is “Relaying Denied.” This is, however, one of the easier bounces to explain.
Relaying Denied means the mail server you’re talking to does not handle mail for the domain you’re sending to. 
Well, OK, but how does that happen?
There are a couple reasons you might get a “Relaying Denied” message, most of them having to do with a misconfiguration somewhere. For whatever reasons, the receiving server doesn’t handle mail for a domain.
DNS records are incorrect. These can be due to a number of things

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Increase in bounces at Y!

I’ve been seeing reports over the last few days about an increase in bounces at Yahoo. Reliable people are telling me they’re seeing some increase in “invalid user” bounces.
You may remember Yahoo announced an overhaul of their mail product back in December. Reliable sources tell me that this is more than just interface revamp. In the back end, Yahoo! is removing older products with few users and security problems. This fits in with the changes CEO Mayer has been making with the company: slim down and stop supporting unprofitable products.
It makes sense that while engineers are looking at the guts of the email program and cleaning up the cruft, they will also disable long unused email addresses. This will result in higher unknown users for some senders.
What’s interesting to me is that the reports are somewhat sporadic. Some senders are seeing a huge percentage of bounces, some are seeing the normal percentage. I expect this difference isn’t anything more than how actively a sender purges based on engagement. Senders that purge unengaged addresses are going to have already removed a lot of the addresses Yahoo! is now purging from their database. Senders that keep sending to their whole list, are going to see a lot of unknown user bounces.
I’ve asked a few folks and people who’ve responded told me that spot checks showed all the addresses turning up as invalid had no engagement for long periods of time.
If you are seeing a lot of bounces at Yahoo! over the last few days, you need to remove those addresses from your lists. I also recommend looking at the engagement statistics of these newly purged recipients. This will tell you, approximately, what an abandoned address profile looks like. You can use that information to make good decisions about purging unengaged users at other ISPs as well. Not only does this lower costs, because you’ll be sending to less non-responsive email addresses, it will also improve delivery at many ISPs.

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