{"id":73559,"date":"2023-08-23T20:34:44","date_gmt":"2023-08-23T20:34:44","guid":{"rendered":"https:\/\/mailrelay.com\/glosario\/email-subject-line\/"},"modified":"2026-10-07T18:38:07","modified_gmt":"2026-10-07T18:38:07","slug":"email-subject-line","status":"publish","type":"glossary","link":"https:\/\/mailrelay.com\/en\/glossary\/email-subject-line\/","title":{"rendered":"Email subject line"},"content":{"rendered":"\n

Before you open an email, the first thing you read is a single line. Based on it, you decide whether to open it now, leave it for later or delete it without a second look. That line is the email subject line.<\/p>\n\n

In a personal email, it just needs to be clear. In an email marketing campaign<\/a>, it also makes the difference. It separates a newsletter<\/a> that gets read from one that gets lost in the inbox.<\/p>\n\n

What is an email subject line?<\/h2>\n\n

The email subject line is the short phrase that sums up what the message is about. It’s also called the subject<\/em> or the subject line<\/em>. In email clients, it appears as a field of its own, right below the recipient.<\/p>\n\n

Technically, it’s one of the message’s headers<\/a>: the one that starts with \u201cSubject:\u201d. It’s not part of the email body<\/a>, but it’s what the recipient sees before opening it.<\/p>\n\n

It’s optional: you can send an email without a subject line. But it’s not a good idea. Many readers ignore those emails, and some filters treat them with suspicion.<\/p>\n\n

What the subject line is for<\/h2>\n\n

The email subject line has three jobs. The first is to inform: it says what the message is about without having to open it. The second is to persuade, because it’s the main reason someone decides to open an email. And the third is to organize: it helps you find the message weeks later with the search bar.<\/p>\n\n

In the inbox<\/a>, the subject line never appears alone. It’s read together with the sender<\/a> name and the preheader<\/a>, the preview text that comes right after it. Together, the three make up a small ad for your message.<\/p>\n\n

\"What<\/figure>\n\n

That’s why it’s best to write them together.<\/p>\n\n

The preheader should complete the email subject line, not repeat it.<\/p>\n\n

What to write in an email subject line<\/h2>\n\n

It depends on the type of message. A work email needs precision; a newsletter needs a hook. Here are some examples:<\/p>\n\n

Email type<\/th>What it should convey<\/th>Sample subject line<\/th><\/tr><\/thead>
Professional<\/td>The topic and, if needed, the action you expect<\/td>Website quote: shall we review it on Thursday?<\/td><\/tr>
Job application<\/td>The position and your name<\/td>Application for UX Designer \u2013 Laura G\u00f3mez<\/td><\/tr>
Newsletter<\/td>The main content of the issue<\/td>5 ideas to boost your Christmas sales<\/td><\/tr>
Promotion<\/td>The offer and its deadline<\/td>Free shipping only until Sunday<\/td><\/tr>
Transactional<\/a><\/td>What happened, straight to the point<\/td>Your order 4521 is on its way<\/td><\/tr>
Welcome<\/a><\/td>A greeting and the next step<\/td>Welcome to Tienda Verde: here’s your 10% off<\/td><\/tr><\/tbody><\/table><\/figure>\n\n

When you reply to an email, keep the original subject line with \u201cRE:\u201d in front. That way the conversation stays grouped and nobody loses track. The same goes for forwarding<\/a> a message, which adds \u201cFW:\u201d or \u201cFwd:\u201d.<\/p>\n\n

How to write a good email subject line<\/h2>\n\n

There’s no magic formula. It’s copywriting<\/a> in very little space. Even so, the subject lines that work best usually follow these guidelines:<\/p>\n\n