Email Subject Lines That Get Opened: Patterns and Length

Email subject lines get opened when they say plainly what the email contains and why it is worth a look today. A fake "Re:" or a deadline that isn't real may win one open. The reader remembers it next time.

An iPhone shows about 40 characters of a subject, and readers take in the preview text underneath in the same glance. Open rates now count emails nobody read, so judge a subject line test on clicks.

The examples are written for a made-up cheese shop in Whitby that emails its customers once a month.

What makes an email subject line get opened

An email subject line is the short line an inbox shows beside or under the sender's name. Readers judge it together with two other lines: the sender name says who is writing, the subject line says what about, and the preview text says why now.

A vague line gives the reader nothing to say yes to. "October newsletter" could head any email from any shop. "Two new blues on the counter from Friday" could only come from this one.

Seven email subject line patterns, with examples

Each pattern below suits a different kind of email; pick by what the email holds, then write the preview text to finish the thought.

Name what is inside

Subject: New in: Stichelton and a Devon goat's cheese Preview: Both arrive on Friday, with tasting notes for each.

This suits a regular newsletter to people who already buy from you. "New in" marks the email as news, and the cheese names do the selling.

Leave your shop's name out. It is already in the sender line.

Put a number on a list

Subject: 4 cheeses for a crowd, all under £6 Preview: A board for ten, ready in ten minutes, with what to pour alongside.

Use a number when the email is a list. It tells the reader how much there is before they open, so the email must hold exactly that many items.

State the offer, then when it ends

Subject: 15% off Christmas hampers until Sunday Preview: The offer ends at 6pm on 29 November. Order online or in the shop.

Put the saving first, where no phone will cut it, and leave the exact end time to the line below.

The deadline has to be the real one, for a legal reason explained further down.

Ask the question the reader already has

Subject: Which cheese goes with port? Preview: Three pairings from the counter, and one to avoid.

A question works when the email answers it in its first lines. If the answer is "come in and find out", the question was bait. Readers learn to skip the next one.

Give the date and time

Subject: Tasting evening this Thursday, 7pm Preview: Twelve seats, £15 each, including a glass of wine.

For events and bookings, the date is the news. A customer who can't come on Thursday still learns that the shop runs tastings, without opening anything.

Say what changes

Subject: From 7 November: new Saturday opening hours Preview: We open at 9 and close at 4. Weekdays stay the same.

Service news needs a plain label, because people need the fact even if they never open the email. Put the date first.

Use their name, with a fallback

Subject: [First name], the Christmas cheese list is ready Preview: Order by 12 December for collection before Christmas.

A first name makes the line feel written for one person, but only if most contacts have one on file.

Set the text that contacts without a name will see, or someone gets a subject that starts with a comma. A name is the simplest use of email personalisation; the same fields can change whole sections of an email.

How long should an email subject line be?

Keep the words that decide the open within the first 40 characters, because that is about where an iPhone cuts the line. Beyond that there is no single best length.

A phone cuts a subject line at a width, not at a set number of characters. We estimated how much of six email subject lines a phone shows, in October 2026. Each line was rendered at the font and width we estimate for iPhone Mail and Gmail on Android. Then we counted the characters before the "…".

Subject line	Characters	iPhone Mail (estimate)	Gmail on Android (estimate)
Christmas hamper orders open today	34	All	All
The same line in capitals	34	31 to 34	All
🧀 Three cheeses for a Bonfire Night board	41	39 to 41	All
New in: Yorkshire Blue and a three-year Cheddar	47	40 to 44	All
Our Saturday opening hours change from 7 November	49	39 to 42	45
Will it be Wensleydale or Lancashire this Christmas?	52	42 to 47	49

Two results change how you write. The same 34 characters took 22% more width in capitals, enough for the narrower iPhone layout to cut them.

So put the word that decides the open first: "Cheddar", "7 November" and "Christmas" were cut on both iPhone layouts.

Desktop inboxes show far more. Gmail on a computer puts the preview text on the same line, after the subject, so a long subject pushes it out of view.

The preview text finishes the sentence

Preview text is the line that follows the subject in the inbox, beside it or underneath. Leave it empty and inboxes show the first text in the email, often a "View in browser" link. Fill it with the fact the subject left out, such as the end time or the price, and never repeat the subject.

What to avoid in email subject lines

Avoid any subject line that promises something the email doesn't contain. Google's email sender guidelines say the subject "should accurately represent the sender identity and message content".

UK advertising rules ask for the same. The Committee of Advertising Practice (CAP) writes them in the CAP Code, and the Advertising Standards Authority (ASA) enforces it.

Avoid	Why	Source
"Re:" or "Fwd:" on an email that isn't a reply	Google gives it as its example of a misleading subject	Google
A false deadline	Saying a sale ends when it doesn't, to hurry the reader	CAP Code rule 3.30
A promise the email doesn't keep	The subject has to represent what the email contains	Google
Hiding that the email is marketing	Unsolicited marketing email must be recognisable as marketing before it is opened	CAP Code rule 2.2

An invented "Re:" also breaks rule 2.2, because it dresses a promotion as part of a conversation.

Rule 3.30 carries the CAP Code's banned-practice label, because consumer law forbids a false deadline outright, whatever the context.

So "Last chance" belongs in the email sent on the last day, and the sale stops when the subject says it does. Read this as a marketer's summary of the codes, not legal advice.

Emoji and capitals in email subject lines

One emoji at the start can label an email, as a cheese does for this shop's newsletter. It should never replace a word.

Each platform draws emoji in its own design. The Unicode Consortium says it has no control over "how emoji appear on their platforms" (Unicode emoji FAQ).

The same FAQ notes that vendors choose which emoji to add in each software release, so an older phone may lack a newer one. Keep the meaning in the words.

An emoji also takes room. In our measurement the cheese took the width of about two and a half letters, enough to tip a line that is near the limit.

A subject written entirely in capitals reads as shouting, and spam filters notice it too. SpamAssassin, an open-source filter that mail servers can run, has a test for it called SUBJ_ALL_CAPS (Apache SpamAssassin rules).

If you use capitals at all, keep them to one short word.

How to test email subject lines when opens mislead

Pick the winner of a subject line test by clicks divided by delivered emails, not by opens.

Apple's Mail Privacy Protection "prevents senders from seeing if you've opened the email message they sent you" (Apple iPhone User Guide). The automatic opens it produces land on both versions of a test and shrink the gap between them.

Click-to-open rate is no way round this, because it divides by those same opens; email marketing metrics sets the rates side by side.

With a few hundred contacts, test one pattern against another; how many people an email A/B test needs shows why.

Email subject lines in MailGraf

In MailGraf, each campaign's Setup step has a Subject and preview text card for the two lines. The Inbox preview beside it shows both in Gmail, Outlook and Apple Mail rows, on a desktop or a phone.

The Subject and preview checks flag a subject under 30 or over 55 characters and a missing or repeated preview text. They also flag capital words of four letters or more, repeated "!" or "?", more than two emoji and any personalisation field without a fallback.

Insert personalisation adds a field such as First name and asks at once for the text contacts without one will see. The character counter then shows "≈", because names differ in length.

With GrafAI on, Suggest both writes ideas for both fields from your email, or from a short description if the design is empty. Each request costs 2 credits, and the monthly plan includes 50 a month. Your fields change only when you click Use (Get subject line and preview text ideas).

To test two lines, click Settings in the top bar, turn on Run an A/B test and choose Subject line. Then switch to Version B on the Subject and preview text card and write the second line (Run an A/B test).

In a subject test, MailGraf names the leader on opens. The table below it lists clicks for each version, so check that row before you keep the winner. Clicks identified as security scanner activity are filtered out on every plan (Read a campaign report).

The phone preview sits on the Setup step of every MailGraf campaign. MailGraf pricing lists the monthly send allowances for using these checks with your own list.