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

  • Failure to remove a MX record after a server is decommissioned;
  • Pointing to a “backup” MX that isn’t configured to act as backup;
  • DNS record changes have not yet propagated

In rare other cases, the DNS records are “correct” but there’s a misconfiguration on the receiving server and it doesn’t “know” that it is supposed to be handling mail for a domain. This can be temporary, if someone publishes DNS records before they finish the server configuration, this message may happen.
In these cases the mail won’t be delivered until the receiver fixes their configuration. It may be reasonable to continue mailing to the addresses, or they can be removed from the list completely.
The other case is that there was an error with the sending server. Some servers cache DNS records for longer than they should. This means that DNS is right but the sending server simply isn’t checking DNS before sending. The sender can fix this by making sure their system isn’t incorrectly caching DNS.
Chances are senders will never see a “Relaying Denied” message. But they do happen in some rare circumstances.
 
 

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Broken record…

The Return Path In the Know blog listed 4 reasons mailing those old addresses is a bad idea.
Ashley, the author, is completely right and I endorse everything she said. (Although I’d really like to hear what happened to the customer that added back all those addresses. What was the effect on that campaign and future email marketing?) As I was reading the article though, I realized how many times this has been said and how depressing it is that we have to say it again. And again. And again.
A number of folks have told me that the reason they don’t pay any attention to delivery professionals is because we don’t provide enough real data. They can show that sending mail to old addresses costs them nothing, and makes them real money.
That’s not really true, though. We do provide data, they just don’t like it so they don’t listen to it. Return Path publishes lots of numbers showing that mailing unengaged recipients lowers overall delivery. I can provide case studies and data but companies that are committed to sending as much mail as possible throw up many reasons why our data isn’t good or valid.
The biggest argument is that they want hard numbers. I do understand this. Numbers are great. Direct and clear answers are wonderful. But delivery is a squishy science. There are a lot of inputs and a lot of modifiers and sometimes we can’t get exactly one answer. The data is noisy, and difficult to replicate. One of the reasons is that filtering is a moving target. Filters are not, and cannot be, fixed. They are adaptive and are changing even between one hour and the next.
Delivery experts are about risk management. They are the parents requiring everyone in the car wear seat belts, even though the driver has never had an accident. They are the fire department enforcing fire codes, even though it’s the rainy season.
Risk management isn’t about the idea that bad things will absolutely happen but rather that it is more likely that a bad thing will happen in some cases.
In this case, it’s more likely that delivery problems will happen when mailing old addresses. And if those addresses aren’t actively contributing to revenue, it’s hard to argue that their presence on a list is more beneficial than their absence.
But I repeat myself. Again.

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Don't think bounce handling is important?

James from Cloudmark has his own insight on spamtraps.

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Bounce handling is hard

Sometimes I find it hard to find a new topic to write about. I decide I’m going to write about X and then realize I did, often more than once. Other times I think I can blog about some issue only to realize that it’s too complex to handle in a quick post. There are concepts or issues that need background or I have to work a little harder to explain them.
One thing I haven’t blogged about before is bounce handling. That particular topic falls into the other category of posts that take a lot of time to write and need a significant amount of work to make sense. I was even joking with my fellow panel members at EEC a few months ago about how that’s a post that so needs to be written but I’m avoiding it because it’s so hard. There’s so much to be conceptualized and explained and I realize it’s not a blog post but multiple blog posts, or a white paper or even a book.
Bounce Rate words on a thermometer or gauge measuring the rate of abandonment as visitors or audience leaves your website or online page or resource
So let’s start with some simple definitions.  Those of you who work at ISPs are probably thinking of bounces in terms of accept than reject, that’s not exactly what I’m talking about here. I’m writing these for senders, who usually call rejects during the SMTP transaction bounces.

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