Subject lines and preview text: asking AI for options

A subject line is a promise about what's inside. An AI tool can write you plenty of options in seconds, but it can't tell which ones keep the promise. You can.

Why the tool leans towards hype

The tool has no view of your reader or your business. If you ask for "catchy" lines, it may reach for urgency and big promises, whether or not they fit your email.

So treat its output as a pile of raw options. Your job is to filter.

How to ask

Do this after the body is finished and checked, not before. Paste the final text, then ask for options that describe it.

Here is the finished newsletter. Give me eight subject lines that plainly describe what's in it. No exclamation marks, no claims about prices or results unless they're in the text, no pretending it's a reply or a personal message.

Asking for a plain description pushes the tool towards honest wording. The email provider Mailchimp makes the same point: "Sometimes, it's better to be direct and descriptive than trendy."¹

Length, punctuation and emoji

Many people read email on a phone, so short lines help. Mailchimp recommends no more than 9 words and 60 characters.¹

Its research also points to no more than 1 emoji at a time.¹ These are one platform's suggestions, based on its own data, and not rules. Tell the tool your limit when you ask, then count the result yourself.

Preview text

Preview text is the short extra line some email programs show beside the subject. Ask for it the same way, and apply the same test. It should add a detail from the email, not repeat the subject or hint at something that isn't there.

The honesty test

Run every option through these questions:

• Is the thing it names actually in the email?
• Is any price, date or deadline in the line correct today?
• Does "free", "last chance" or "ends tonight" match what's really on offer?
• Does it pretend to be a reply, an invoice or a personal note when it isn't?
• Would the reader feel tricked after opening it?

Rules exist here as well as manners. In the United States, a summary of the CAN-SPAM Act lists subject lines that are relevant to the offer and not deceptive among its content requirements.² Other countries have their own rules. The regulators' pages are collected in where the official sources are.

In Australia, the consumer regulator says it makes no difference whether a business intends to mislead.³ Claims in an ad also need reasonable grounds behind them.³ A subject line makes a claim like any other. A tool that wrote it won't take the blame.

Letting your readers decide

If you can't choose between two options, test them. Mailchimp notes that "A/B and Multivariate tests reveal how small differences impact performance."¹ Many email platforms offer something similar. Both versions must still pass the honesty test, since a test picks the more effective line, not the more truthful one.

Finally, read the winner out loud next to the first paragraph of the email. If someone opened it expecting the subject and got the body, would they feel they'd got what was promised? If not, rewrite the line, or ask the tool again with a tighter brief. Then move on to the pre-send fact check.