Steve Atkins
Are you seeing this bounce message when trying to send mail to Yahoo subscribers?451 Message temporarily deferred due to unresolvable RFC.5321 from domain; see https://postmaster.yahooinc.com/error-codesAnd you’ve checked and confirmed that your sending domain seems to resolve for you, so you’re wondering, what the heck is going on and what do I do about it? If so, Steve Atkins has got you covered. Over on the Word to the Wise blog, he explains how Yahoo is looking for an SOA record (Start of Authority) in DNS and depending on how your DNS and delegation are configured, you could be misconfigured in a way that most don’t notice, but would fail this check.Click on over to Word to the Wise to learn more. Thank you, Steve, for clearing this up! It’s a tricky one.
One of the most common refrains I hear from folks with delivery problems is that the filters must have changed because their mail suddenly started to go to the bulk folder. A few years ago, I posted about how even when there is no change in the sender’s behavior, reputation can slowly erode until mail suddenly goes to the Gmail bulk folder. Much of that still applies – although the comments on pixel loads (what other folks call ‘open rates’) are a bit outdated due to changes in Gmail behavior. While it is often true that reputation drives sudden delivery problems there are other reasons, too. Filters are always adjusting and changing to meet new challenges and threats. We’re seeing these changes rolling out at some of the consumer mailbox providers. Steve recently wrote about changes that Yahoo! was making related to domain existence. He also posted about Microsoft getting
As a consumer there are several different sorts of email address that are described as “disposable” or “temporary”. Some of them are what we might call tagged addresses – addresses that are unique, created to be given to a specific vendor. If it’s misused by the vendor, or if it’s leaked to spammers, then the address can be disabled, either by rejecting or by silently discarding mail sent to it. Others are created for a specific use, and will only be briefly valid, either for a single email or for a short period of time (ten minutes, an hour, something like that). They typically don’t have any connection to a users “real” email address, and are just accessed via a web page. A user might use this when they’re being required to give an email address to access some sort of service but there’s no ongoing use of that email
Trekkie Monster. He’s obsessed by social media and isn’t owned by Children’s Television Workshop. What is a Cookie? I’m not talking about biscuits, nor about web cookies, at least not exactly. When you’re talking to a protocol developer a cookie is a thing you’re given, that you hang on to for a while, then give back. If you leave your suitcase with your hotel concierge they’ll give you a paper ticket with a number on it. That ticket and the number on it aren’t of any intrinsic value, nor do they really mean anything. The only thing you can do with it is give it back to the concierge to get your suitcase back. The ticket is a cookie. Conceptually a cookie isn’t something that’s meaningful except when you give it back to whoever gave it to you – so if you’re a client program and a server sends you
Seen this recently? 451 Message temporarily deferred due to unresolvable RFC.5321 from domain; see https://postmaster.yahooinc.com/error-codes This is Yahoo doing some extra work to identify that the 5321.From domain1 of the mail is acceptable to them. Yahoo are going (slightly) beyond what’s required for the return path to be valid in SMTP terms. SMTP just requires that the return path be syntactically valid – i.e., looks like an email address – and that it be deliverable. The basic DNS check you might do would be to check if the right-hand-side of the email address has an MX record2. So for a bounce address of bounces@email.example.com you’d check to see if email.example.com had an MX record. Yahoo want to also check that it looks like a legitimate address in another way, that the organizational domain of the right-hand-side looks legitimate. The organizational domain is what you might think of as a “domain”
Several times recently I’ve heard about something unusual happening email delivery-wise at academic domains that was new, and wasn’t being seen at non-academic domains on the same lists. Most recently it was aggressive following of all links in an email at delivery time, seen at several .edu domains, all using the same mail provider. Not that unusual a thing in itself, we know that corporate malware filters have done this for a while. But this seemed more aggressive than just “this mail looks iffy, lets sample a few links and look for malware”, and the new behaviour was only being seen on .edu recipient domains, not on any of the non-academic domains using the same mail provider. If any .edu postmasters can explain, please, do, but my speculation is that one big difference between academia and the corporate environment is how much control the IT security folks have over recipient
There is an ever increasing amount of spam I am getting from various companies asking for links here on WttW. The Answer is No. We do not have paid links. We do not have sponsored posts. Any links on the site are done at our whim and because we have something to say about your company. The only place we offer links is on the ESPs and Purchased Lists post. And, I gotta tell you, if you buy my address and then send me spam asking to be added the answer will be No because it’s clear you don’t have a policy that meets the criteria for addition. And, yes, folks have done this. We do not work with spammers, and we certainly don’t promote their services, not publicly and not to our clients.
These last few years have been something, huh? Something had to give and, in my case, that something was blogging. There were a number of reasons I stopped writing here, many of them personal, some of them more global. I will admit, I was (and still am a little) burned out as it seemed I was saying and writing the same things I’d been saying and writing for more than a decade. Taking time off has helped a little bit, as much to focus on what I really want to talk about. It helps, too, there are a lot more deliverability resources out there than when I started. I don’t have to say it all, there are other voices (and perspectives!) that are adding to the collective understanding of delivery. That’s taken some of my (admittedly internal) pressure off from having to write about specific things to explain, educate and
When we’re looking at the technical details of email addresses there are two quite different contexts we talk about. One is an “821 address” or “5321 address”. This is the email address as it’s used by the SMTP protocol, as part of the “MAIL FROM: ” or “RCPT TO: ” commands sent to the mailserver. It’s defined in RFC 821, now updated by RFC 5321, hence the name. If someone mentions the “envelope” or they’re talking about “bounce addresses”, this is the sort they mean. We’re not talking about them in this post. The other is an “822 address” or a “5322 address’. They’re the ones the recipient sees in the To: or From: headers. They’re named after their RFC, RFC 5322. This is the sort of email address most folks mean by default, unless they’re explicitly talking about the envelope of an email, but if someone describes an email
It looks like Microsoft are getting pickier about email address syntax, rejecting mail that uses illegal address formats. That might be what’s causing that “550 5.6.0 CAT.InvalidContent.Exception: DataSourceOperationException, proxyAddress: prefix not supported – ; cannot handle content of message” rejection. Why do we care? It’s good to send syntactically valid email in a warm fuzzies sort of way – it shows we know what we’re doing, and aren’t dodgy spamware – but it’s increasingly important to delivery as mailbox providers are tightening up on their syntax checks. But why are mailbox providers doing that? One reason is that authentication tech like DKIM and DMARC is built around them only being applied to email. Not to messages that kinda look like email. There are ways to bypass DKIM protections by sending invalid messages. As one example, if you send multiple copies of the From: header with different values a DKIM checker