Adding your domain to the public suffix list might break all your email.
Are Complaints Weighted?
I’ve been doing a lot of my question answering over on the Email Geeks slack and have decided to bring some of the answers over here. Today’s question: My ESP provides a dashboard of spam complaints. How should I be looking at the data? Are some complaints more important than others? The spam complaint dashboard is a record of the feed back loop messages (FBLs) that an ESP has...
Diagnosing Hard Bounces
A very short post about diagnosing hard bounces, because I’ve had to give the same advice to a dozen folks over the past few months. When you’re diagnosing and mitigating hard bounce rates the first thing you’ll see is your ESPs dashboard or reporting. It’ll tell you how many emails you sent bounced, and how that number has changed over time. A useful start. But a hard...
Effects of the Yahoo and Google Changes
In October 2023, Yahoo and Google announced new standards for sending bulk mail to their systems. For bulk senders these changes included requiring aligned authentication and publishing a DMARC record and complying with the List-Unsubscribe RFC. The ISPs also formally announced complaints must stay below a threshold of 0.3%. At the time of the announcement, they said enforcement would start in...
Stop using Entrust for your BIMI Certificates
You should probably stop using Encert for BIMI certificates. Apple definitely think you should.
Tracking link maths
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...
There’s text and then there’s text
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...
Your bounce classification is a bit rubbish
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 care about SPF alignment?
Do we really care whether our SPF email authentication is aligned?
Comparing DKIM keys
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...