How to write email subject lines that earn the open and the click.

A good email subject line is specific, front loaded, honest and paired with a preheader that adds something new. On a phone you may get only 33 characters before the cut, so this guide on how to write email subject lines starts with one question: what single fact does this reader need before deciding to open? At EmailMarketingAgency.com we write two subject lines for each of the 8 campaigns we run for a client every month, one per side of an A/B test. Below: a 6 step method, length data by device, formatting rules, preheader pairing, honest testing and 30 original examples.

How to write email subject lines in 6 steps

1. Name the job of the email in three words. "Sell the sofas." "Book winter sites." If you cannot say it that briefly, the email is doing too much.
2. List every fact a reader might ask about. Product, price, percentage, date, deadline, place, distance, size.
3. Pick the one fact that changes the decision. For a sale, the offer and end date. For a launch, the product plus one proof. For a campground, a place or number the guest can picture.
4. Put that fact inside the first 33 characters. Start with the noun or the number, not your brand name. The from name already says who is writing.
5. Write the preheader as line two. Add what the subject left out: the proof, the deadline, or the answer to "so what?"
6. Draft a second version that changes one idea, check both against the honesty rules below and preview them on a real phone.

Most weak subject lines fail at step 3: they reach for a mood ("Big news!") instead of a fact the reader can check.

How long should an email subject line be?

No single number is correct, because each inbox app cuts the line at a different point. The most useful public data we know of is EmailToolTester's device test, which sent the same pangram to each inbox and counted what stayed visible.

Narrow letters such as "i" fit more per row than wide ones such as "M", so read these as ranges. Our rule from the data: the key fact lives in the first 33 characters, the full subject stays under 50, and the first 37 characters of the preheader make sense alone. That is tighter than the ceiling in Mailchimp's subject line best practices, no more than 9 words and 60 characters, because the phone is where lines get cut.

Here is what front loading changes, in an illustration based on a snowbird campaign we wrote for Lake Buchanan RV Resort in Burnet, TX (the principle, not the line we sent):

• Brand first (57 characters): "Lake Buchanan RV Resort is now taking winter reservations" is cut to "Lake Buchanan RV Resort is now ta" in the Gmail app on a Pixel 7. A name, no reason to open.
• Fact first (31 characters): "Winter sites right on the water" fits on every tested phone, and the resort name is already in the from line.

How should you format an email subject line?

Format decides whether a line reads like a note from a business or like junk mail. Mailchimp's guidance also suggests no more than 3 punctuation marks and no more than 1 emoji per subject line. Our house rules go a little further:

• Sentence case by default. Capitalize the first word and proper nouns, the way people type to each other. Capitalizing Every Word reads like a banner ad and buries the product name that should stand out.
• Digits, not spelled out numbers. "42 new sites" is shorter than "forty two new sites", and a digit stands out in a row of letters.
• Punctuation that does a job. A colon splits a label from the fact ("First look: spring patio sets"). A question mark belongs on a real question. One mark per job is plenty.
• Relevance over a first name. A name merge tag is the most copied personalization trick. A line written for a segment says more: "Open house Saturday in Plano" for subscribers near Dallas, "Your plan renews March 1" for annual customers. Audience segmentation is part of every campaign we run, so the subject can change by segment.
• Curiosity only with a payoff. A teaser such as "The question we get every week" works when the preheader hints at the answer. A teaser with no clue in either line reads as clickbait.

How should a subject line and preheader work together?

Most inboxes stack three lines: the from name, the subject and the preheader. The preheader, also called preview text, is the lighter line shown beside or under the subject. Mailchimp's help center explains that if you leave it unset, email clients pull in the first part of your message, which can be a "View in browser" link or stray code. Apple Mail on an iPhone showed up to 99 preheader characters in EmailToolTester's test, which is a lot of space to leave to chance.

Read all three as one message, and treat the subject and preheader as one sentence split across two rows. The subject earns attention; the preheader turns it into a click. Four pairings cover almost every campaign we write:

We wrote these sample pairs for this guide. Three rules keep any pairing working:

• Never repeat the subject in the preheader. Two lines should carry two pieces of information.
• Hold the preheader to the same honesty standard. Readers judge the email by both lines.
• Use the platform field, then guard it. Klaviyo, Mailchimp and HubSpot all have a preview text field. If your text is short, add invisible spacer characters after it so body copy does not leak into the preview.

Eight subject line formulas from real campaigns

These are the patterns we use most, each tied to a campaign we designed and wrote. We cannot publish results for client work, so you get the reasoning, not open rates. The finished emails are on our email campaign examples page.

The thread through all eight: a concrete noun or number beats an adjective. "Huge savings" asks for trust. "Up to 25% off consoles" lets the reader check. See how these hooks fill a season on our campground and RV park email marketing page, or the deadline formula in context on our SaaS email marketing page.

What should you leave out of a subject line?

Some tricks lift opens once, then cost you trust, complaints or legal exposure. We skip all of these:

• Fake "Re:" or "Fwd:". Google's email sender guidelines tell senders not to start a subject with Re: or Fwd: unless the message really is a reply or forward.
• Disguised promotions. "Your order update" on a sale email. Readers who feel tricked may report spam instead of unsubscribing.
• Urgency with no end. "Last chance" with no date. If a real cutoff exists, name the day and time zone.
• Shouting. All caps and rows of exclamation points read like junk mail, even when a filter lets them through.
• Emoji doing the talking. One emoji that adds meaning can be worth a test. Google's guidelines warn against using emojis or other nonstandard characters to imitate graphic elements in messages.
• Merge tags with no fallback. A first name field with no default can greet contacts with "Hi ,". Set a fallback or skip it.

The legal floor is short. According to the FTC's CAN-SPAM compliance guide:

"The subject line must accurately reflect the content of the message." (FTC, CAN-SPAM Act: A Compliance Guide for Business)

The FTC adds that each separate email in violation can bring penalties of up to $53,088. Our CAN-SPAM compliance checklist covers the rest, from postal address to opt out.

How do you A/B test subject lines without fooling yourself?

A subject line A/B test sends versions to small slices of your list, then sends the winner to everyone else. Mailchimp lets you test one of four variables (subject line, from name, content or send time) with up to 3 variations, choosing the winner by open rate, click rate or total revenue. Klaviyo offers open rate, click rate or placed order rate and recommends only 2 variations.

The trap is the open rate. Apple says that with Mail Privacy Protection on, remote content is downloaded privately in the background when a message arrives, and Klaviyo's help center confirms its open rate tests count those opens. A line can "win" because more of one group reads on Apple Mail. So we follow four rules:

1. Test one idea per campaign. Number versus no number, offer first versus product first, place versus benefit.
2. Judge on clicks or orders where the platform allows it. Opens are a tiebreaker at most.
3. Respect small lists. A gap of a handful of clicks is noise. Repeat an idea across several sends before calling it a rule.
4. Log every result: both versions, the idea, the metric and the lesson.

These rows show the format, not real results. A few months of this tells you more about your list than any benchmark. For which numbers to trust, see our guide to email marketing metrics.

30 email subject line examples by campaign type

Every example below is original and written for this guide. None comes from a client campaign, and no performance data sits behind them. The character count shows which fit the 33 character phone window. Swap in your own products, dates and numbers; a subject line only works when its fact is true.

Product launches

Sales and promotions

Seasonal and holiday sends

For the dates worth building these around, see our 2027 email marketing calendar.

Campgrounds, hospitality and local events

B2B and SaaS

Newsletters and win back emails

Subject line checklist before you schedule

• The key fact sits inside the first 33 characters.
• The full line is under 50 characters, or its end can be cut safely.
• The preheader adds new information and reads well in its first 37 characters.
• Sentence case, digits for numbers, at most one emoji.
• Every price, percentage and date in the subject is true inside the email.
• Deadlines name a day and a US time zone.
• No fake Re: or Fwd:, no all caps, no disguised promotion.
• Every merge tag has a fallback value.
• The B version changes one idea, and the winning metric is clicks or orders.
• You previewed it on a phone in at least Gmail and Apple Mail.

Rather hand subject lines to someone else?

$1,000 a month covers 8 finished campaigns, each with its own preheader, copy, design, QA and a subject line A/B test, and you approve every email before it goes out. The full scope is on our pricing page, and how we match your voice is on the email copywriting services page. Want a second opinion on your current subject lines? Our free email audit reviews your recent campaigns and includes a sample campaign calendar, with no cost and no obligation.

Frequently asked questions