Technical

When you query DNS for something you ask your local DNS recursive resolver for all answers it has about a hostname of a certain type. If you’re going to a website your browser asks your resolver for all records for “google.com” of type “A”1 and it will either return all the A records for google.com it has cached, or it will do the complex process of looking up the results from the authoritative servers, cache them for as long as the TTL field for the reply says it should, then return them to you. There are dozens of different types of records, AAAA for IPv6 IP addresses, MX for mailservers, TXT for arbitrary text, mostly used for various sorts of authentication (including SPF, DKIM and DMARC). And then there’s CNAME. CNAME stands for “Canonical Name” and means “Go and ask this different question instead”. If you have a DNS record

Learn what is Microsoft Smart Network Data Services (SNDS), including how to utilize SNDS data to improve your email program. The post What Is Microsoft Smart Network Data Services (SNDS) and Do I Need It? appeared first on SendGrid.

Staying compliant in today’s email world is a must. We hear insights from Anne P. Mitchell, who helped author the CAN-SPAM Act of 2003. The post Ask the Expert: Anne P Mitchell, CEO and President, Get to the Inbox by ISIPP SuretyMail appeared first on SendGrid.

Eventually our subscribers won’t want our email in their inbox any more. They can stop the mail either by unsubscribing from it, or by marking it as spam. We’d far rather they do the first so we should make it as easy as possible for them to unsubscribe. Also in most jurisdictions you’re legally required to offer a functional, easy to use unsubscription channel. So, how to do that? There are a few different ways to accept unsubscription requests, and most legitimate bulk mail should offer several of them. Reply to unsubscribe The recipient replies to the email, the person handling replies removes them from the list. This is a problematic way of handling unsubscription requests. On the one hand, sending mail that recipients can’t reply to, or where replies are bounced, responded to automatically or silently discarded is fairly recipient-hostile. It’s better if those replies go to a customer

I stumbled across this story again this morning, and it’s such a lovely delivery yarn I thought I’d share it. It’s from Trey Harris, and it’s set in the mid 90s. Here’s a problem that *sounded* impossible… I almost regret posting the story to a wide audience, because it makes a great tale over drinks at a conference. 🙂 The story is slightly altered in order to protect the guilty, elide over irrelevant and boring details, and generally make the whole thing more entertaining. I was working in a job running the campus email system some years ago when I got a call from the chairman of the statistics department. “We’re having a problem sending email out of the department.” “What’s the problem?” I asked. “We can’t send mail more than 500 miles,” the chairman explained. I choked on my latte. “Come again?” “We can’t send mail farther than 500

I’ve heard quite a bit of concern about what iOS 17’s automatic removal of click-tracking parameters means, but less discussion of what it actually does. Broadly it’s Apple trying to improve user-privacy by making it harder to do cross-site tracking at scale. Cross-site tracking is the basis of a lot of privacy-violating tracking technologies, and tracking parameters added to links evade Safari’s technologies that mitigate tracking via cross-site cookies or other forms of session storage. (As partial compensation, Apple is supporting Private Click Measurement. That’ll allow ad click measurements without sending PII to the advertisers.) But, what does it actually mean? I’ve not seen much in the way of documentation, so I built a test harness, installed an iOS 17 developer beta on a spare iPad and looked at what it does. The test setup is very, very simple. I have a custom webserver that accepts clicks and logs the

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

Read about what a webhook is, how it can be used with your apps, and how to get started using webhook APIs. The post What’s a Webhook? appeared first on SendGrid.

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”

Learn about the differences between ports 465 and 587, why there’s so much confusion around the ports, and how to best use these ports. The post SMPT Port 465 and Port 587: What’s the Difference? appeared first on SendGrid.