How long does a tracking link need to be? Let’s make it interesting, and say we want to be able to have a unique tracking link for every single atom in the observable universe. That’s about 1080 unique links. One hundred novemdecillion exa-links. 100,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 If we have that many customers...
If you want to send someone an email with some text in it there are quite a few different ways you can do it. The main differences are the ways the text is packaged up in MIME entities to be sent. text/plain This is the simplest sort of text you can send. If you send a simple email with many desktop mail clients, this is what you get. You can’t include images, you can’t choose fonts...
When a mailbox provider rejects or defers an email it sends back a message explaining why. Those messages begin with a three digit number (starting with a “5” for rejections and a “4” for deferrals), followed by text that explains why the mail wasn’t accepted. That text often contains a link to follow for more information, or a mailbox provider specific code you can...
Do we really care whether our SPF email authentication is aligned?
Sometimes we have a client who has done something wrong when setting up authentication. Their DKIM signing fails due to something being wrong with the public key they’ve published. The published key looks fine, by eye. It’s got all the fields it should have, but diagnostic tools give inscrutable error messages. If you’re lucky, “This doesn’t seem to be a valid RSA...
We use DNS a lot in email, particularly for authentication, so diagnosing why DNS isn’t returning what we expect it to is a pretty common challenge. And DNS responses aren’t exactly the clearest thing to understand. There are two types of DNS server we need to know about. When we publish DNS records for our own domain we add them to a nameserver that is authoritative for our domain...
Why is designing spam filters like designing bear-proof trash cans?
Jody asks “Are ‘prefetch opens’ and ‘proxy opens’ the same thing?” Non-human opens An “open” is just someone (or something) fetching a remote image. A non-human-interaction (NHI) open is where some sort of automation fetches the image without human interaction – i.e. it’s fetched when the automation feels like it, not triggered by a user...
If you’re using sendy and you’ve found that RFC 8058 one click unsubscribe fails – or, worse, seems to work but doesn’t actually unsubscribe the user – you should take a look at James’ workaround.
Lots of times I see someone asking a question and they talk about their sending domain. And it’s sometimes not 100% clear which domain they mean by that – and when we’re talking about alignment and reputation it can make a difference. So here’s a list of (some of?) the different places a mailserver uses a domain. Hostnames Machine Hostname: What the operating system...
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