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.

Goodbye Mr. Ebert
DNS, SERVFAIL, firewalls and Microsoft

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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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More on the Yahoo exploit

Exacttarget’s Carlo Catajan talks about the Yahoo exploit. My own mailbox seems to indicate this hole is closed.

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Data hygiene and bouncing zombies

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 don’t always deactivate addresses on the schedules they publish? Because I have seen addresses not be deactivated.
I have addresses in a lot of places that I go for long periods of time not checking. It’s rare that they’re taken from me or reject mail – most of the time they’re special test addresses I use when diagnosing issues. This post is based on my experiences with those addresses and how abandoned addresses are treated at some ISPs.
For Gmail I have two examples of addresses not being deactivated.
In July 2011, we set up a test address to look at how Gmail was handling authentication. We sent a matrix of different test emails to it, with valid and invalid SPF and DKIM signatures. We pulled the data from the account. I don’t know for certain when the last time I logged in, but it was August or September of last year. So we have an address that has been dormant since September 2011.
I just sent mail to the account and google happily accepted it.
Mar  2 07:03:22 misc postfix/smtp[11770]: 11CA12DED3: to=<wttwtestacct@gmail.com>, relay=gmail-smtp-in.l.google.com[74.125.127.27]:25, delay=1.8, delays=0.25/0.02/0.56/0.93, dsn=2.0.0, status=sent (250 2.0.0 OK 1330700602 x8si8608852pbi.66)
I have another google account (apparently) that my records show I set up sometime in 2010. The login info was saved October 2010. I don’t know when the last time I logged in was, but given I’d forgotten the existence of the account it’s a good bet that it has been more than a year. That account is also accepting mail as of today.
Mar  2 07:06:25 misc postfix/smtp[11836]: 8D90C2DED3: to=<phphendrie@gmail.com>, relay=gmail-smtp-in.l.google.com[74.125.127.27]:25, delay=1.6, delays=0.26/0.02/0.68/0.66, dsn=2.0.0, status=sent (250 2.0.0 OK 1330700785 a8si4075740icw.96)
For Hotmail I also have quite a bit of history and information. I signed up for my first Hotmail account in 1997. That was an account I used the address to post to usenet, but I didn’t actually use it for mail. I’d check it occasionally (usually when someone said in the newsgroup that they were going to email me) but it wasn’t an address I used regularly. As I moved from posting regularly in usenet, I started checking that account even less.
For a while, if I went more than 6 months checking my Hotmail account they would make me “re-claim” it. What would happen when I’d log in is I’d get a message along the lines of “well, we disabled this account due to inactivity, do you want it back?” I’d say yes, have to go through the setup process again and it would be my account. Mail was deleted during the disabling, and I am guessing they rejected anything new going to that account. I went through this dance for 4 or 5 years. I even had my calendar set to remind me to login every 6 months or so. There was some sentimental value to the address that kept me logging in. I have that same username at every major free ISP: Gmail, Hotmail, Yahoo and AOL, so it’s “my” address.
About 6 or 7 years ago, that behavior changed. I stopped getting the request to reclaim my account. Instead I could just log in. I’d still have mail (mostly spam as the address is on *lots* of lists and millions CDs). I still check it irregularly. I don’t have any idea when the last time I checked it was, but I think it’s been since at least November and probably longer back than that. Hotmail is still accepting mail for that address as well.
It’s anecdotal evidence, at best, but it ‘s the type of evidence that is acceptable even when it’s anecdotal. There are some addresses that are abandoned for long periods of time at the free mailbox providers and they’re are not all automatically pulled from the ranks of active addresses.
What does this mean for senders? It means that data hygiene has to go beyond just removing addresses that bounce. ISPs are not disabling addresses consistently enough for marketers to be able to trust that all addresses on their list are active just because they are accepting email.
This is the root of the recommendation to put in a hygiene program, this is why senders need to look at who is actually engaged with their brand and make some hard decisions about shooting zombies in the head.

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