- Two calls to action in one email produce fewer total clicks than one, in every split test we have run.
- The preheader is a second headline and most senders waste it on the first sentence of the email.
- Every email must make sense with images blocked, in dark mode, and at 4.5:1 contrast.
- A ten-minute pre-send test across two providers has caught something in roughly one send in four.
- Report clicks, conversions and revenue per recipient; open rate stopped being a metric years ago.
Every rule below exists because we broke it once and had to explain the result to a client. They apply to newsletters, campaigns and automated sequences alike.
1. One idea, one action
An email with two calls to action gets fewer clicks in total than an email with one, in every split test we have run. If there are genuinely two things to say, send two emails.
2. Write the subject line last
Subject lines written first describe what you intended to write. Written last, they describe what you actually wrote, which is what the reader will find. Keep them under about 45 characters so they survive truncation on a phone, and avoid words that trigger scepticism, free, urgent, last chance, unless they are literally true.
3. Use the preheader deliberately
The preview text next to the subject line is a second headline, and most senders leave it as the first sentence of the email. Write it. It roughly doubles the information the reader has before deciding.
4. Front-load the message
Many recipients read only the preview pane. Whatever matters most goes in the first two lines. Pleasantries, context and background go below, or nowhere.
5. Write as a person, from a person
Send from a named human at your domain, not noreply@. Write in the first person. Reply-to should reach an inbox someone reads. A large share of the value in a small business newsletter arrives as replies, and noreply throws that away.
6. Assume images are blocked
A meaningful proportion of recipients see no images by default, and an image-only email looks to them like an empty message. The email must make sense as text. Alt text on every image, and never put the offer inside a picture.
7. One column, generous type
Multi-column layouts collapse unpredictably. Use one column, 16px or larger body text, and a link style visibly different from body text without relying only on colour. Buttons at least 44 pixels tall so they can be tapped.
8. Check the links, then check them again
Every link, in a real client, from a real device. Broken and wrong links are the most common error we have shipped and they are entirely preventable. Add UTM parameters consistently, the same naming scheme every time, or your reporting is fiction.
9. Contrast and colour
Body text needs at least 4.5:1 contrast against its background. Dark mode inverts many email clients unpredictably, so test in it. Light grey on white is unreadable in one mode and invisible in the other.
10. One-click unsubscribe, honestly implemented
Required by the major mailbox providers and correct anyway. The link works in one click, it is visible without hunting, and the request is honoured within a day. Hiding it converts an unsubscribe into a spam complaint, which costs far more.
11. Test before send, every time
Our pre-send test: send to two real inboxes at different providers, open on a phone and a laptop, check in dark mode, click every link, read the plain-text version, confirm the from-name and reply-to. Ten minutes. It has caught something in roughly one send in four.
12. Report clicks and revenue, not opens
Open rate is unreliable and gets less reliable every year. Report clicks, conversions and revenue per recipient. If a client insists on open rate, show it beneath the numbers that mean something and explain why.
We write, build and send campaigns for clients across four countries, templates that survive dark mode, and reporting that shows revenue rather than opens.
A note on templates
Build one template and reuse it. Every additional layout is another thing to test in a dozen clients, and the variety buys nothing. Readers do not notice or reward design novelty in email. They notice whether the message is clear.
The template needs a plain header with your name, a single content column, a button style, an image style with sensible default widths, and a footer with your postal address, the unsubscribe link and a sentence explaining why this person is receiving it. Get that right once and every subsequent send is a writing task rather than a build task, which is the only way a small team keeps sending at all.
The pattern behind the list
Nine of these twelve are about respect: for the reader's attention, their inbox, their device and their ability to leave. That is not a moral point, it is a deliverability one. Mailbox providers measure engagement and complaints directly, so being annoying is expensive in a way it was not five years ago.
The other three, front-loading, one action and testing, are about the email doing its job in the four seconds it actually gets.
What we stopped doing
Countdown timers, which break more often than they work. Personalised subject lines using a first name, which now read as automation rather than familiarity. GIF-heavy layouts, which are slow and inaccessible. And re-sending a campaign to non-openers with a new subject line: with open tracking as unreliable as it now is, you are largely mailing people who already read it.
Where the list came from, and who should use it
This started as a page in our internal handover pack, which is why it reads as rules rather than principles. New writers on our team work from it for their first few sends, and clients who run their own campaigns after we hand an account over get a copy.
If you only adopt three, take the pre-send test, the single call to action and the preheader. Those three catch the most damage for the least effort. The sequences these messages usually sit inside are covered in email automation, the wider channel order in full-funnel sequencing, and if you would rather hand the sending over entirely, that is what our email marketing service does.
Questions
What is a good email subject line length?
Under about 45 characters so it survives truncation on a phone. Clarity beats cleverness: a subject that says what is inside outperforms one that teases it in almost every test we have run.
Should marketing emails be plain text or designed?
Lightly designed, one column, and readable as plain text if images fail. Heavily designed emails do not outperform simple ones for most small businesses and are far more likely to render badly.
What day and time should I send?
Consistency matters more than the specific slot. Pick a day and time, keep it, and test alternatives one at a time over months. Tuesday morning is a fine default with no special magic to it.
How do I reduce unsubscribes?
Segment so people receive things that apply to them, keep a predictable rhythm, and offer a way to receive less rather than nothing. Most unsubscribes are relevance problems wearing a frequency costume.