Articles
How email really works, told in short reads.
Short posts: the history, the lists that quietly decide delivery, the rules, the costs, and the numbers.
Supabase stops at 2 emails an hour. Here's what's going on, and the quickest way past it
Your fourth sign-up gets "email rate limit exceeded". That's the built-in sender doing exactly what it says. Two ways out, one of them a short Edge Function.
Choosing a senderSendGrid's free plan is gone. What a small app can use for sign-up emails now
The 100-a-day plan that powered a decade of side projects became a 60-day trial. Here is what is left, and what each option asks of you.
Sign-up hygieneBlocking throwaway emails at sign-up, without maintaining a list yourself
Disposable inboxes cost you free-tier abuse and dead newsletter addresses. Here is how to stop most of them in one request, and where to stop trying.
HistoryEmail is older than the web. Here are nine frames of how it changed.
It began as a way for two programmers to leave each other a note on a shared machine. Then everything happened.
DeliverabilityThe secret lists that decide whether your email exists
Your message can be perfect and still never reach an inbox, because of a list you have never heard of.
Self-hostingWhy nobody can run their own mail server anymore (almost)
In the late nineties it was a weekend project. Today one bad neighbour on a shared IP address can end it.
HardwareSpam filters you can rack in a data centre, and what they cost
Three appliance families, their list prices, and why the bill is never just the box.
SoftwareSpam filters you install, subscribe to, or never see
Free open-source engines, per-user cloud add-ons, and the filter already sitting in the inbox you use.
VolumeAbout 390 billion emails a day. Where do they all go?
Roughly 48 for every person on Earth, every single day. A large share of them is machine-made.
ProvidersA handful of companies sit in front of most of the world's inboxes
Gmail, Outlook and Yahoo decide, in milliseconds, what you see first. Here is how much they handle.
CountriesWhich countries write the most email? The numbers are rougher than you think
One country tops the per-person charts, another tops the totals, and the sources don't agree on either.
AuthenticationSPF: the guest list for every server that claims to speak for you
One DNS line decides whether a stranger can send mail in your name. Five things to know before you touch it.
AuthenticationDKIM: the wax seal that travels with your message
A signature no one can forge without your private key, and why it breaks when a mailing list edits your mail.
AuthenticationDMARC: the rule that tells mailbox providers what to do with fakes
Three policies, one report address, and why spoofers tend to go quiet once you publish it.
DeliverabilityWhy good email still lands in spam
Usually it is not the words. It is the sender, the links and the people who press the spam button.
RulesGmail and Yahoo changed the rules in 2024. Here is what they require
Five thousand emails a day is the line. Above it, authentication and one-click unsubscribe stop being optional.
ConsentThe unsubscribe link: the one button every newsletter is supposed to have
Why it exists, what the rules say in the big markets, and why hiding it costs more than keeping it.
CategoriesTransactional or marketing? The line that changes how your email is treated
A password reset and a sale announcement can come from the same app and still follow different rules.
ProtocolsSMTP is from 1982. Why more apps now send email over HTTPS
A protocol built for relays between trusted servers is a poor fit for a web app that needs a message sent in one request.
AgentsBots need an inbox too. How an agent signs in with a code
No password, no browser, no human in the loop. An email code is the oldest trick that still works for software.
CostsWhat 100,000 emails really cost across providers
Per-message prices look tiny until you add the monthly fees, the minimums and the extras nobody mentions.