How to write a subject line for an email to a business

What the reader sees before they open it

Before anyone reads your email they see three things in their inbox: who it's from, the subject line and a line or so of preview text. On a phone that's most of what fits on the screen, and it's all they have to decide whether to open it now, leave it for later or delete it. A good subject line only works if the other two are pulling in the same direction.

The sender name is the display name attached to your address, and you set it in your email account's settings. Use your own name and your business, such as "Mel Tran, Eastside Cleaning". Google's sender guidelines say a display name should identify the sender and should never be used to deceive the reader. They also say it shouldn't carry subject or message content like "Quote inside" or "URGENT", shouldn't include the recipient's name and shouldn't imply a reply or thread, such as a "(2)" after the name.

The preview text is usually the first words of your email. If those words are "Hi Jo, I hope this email finds you well", that's what shows next to your subject. Make your first sentence the one about their business so the preview backs up what the subject said. How much of the subject and preview shows depends on the app and the screen, so put the words that matter at the front and assume the end might be cut off.

Plain and specific beats clever

Whoever looks after suppliers for a business sorts their inbox quickly, between jobs and phone calls. A plain subject tells them in a few words what's inside, so they can decide in a second whether it's for them. It also reads like an email from a real person, because that's what it is.

The useful words are usually what you do and the thing of theirs it relates to: their buildings, their suburb, their venue or their office. You don't need a hook. Here are some made-up examples.

Look at what the plain versions leave out. There's no price, no "free", no question designed to make the reader curious and no capital letters shouting at them. A subject like "Are you protected?" only gets opened because the reader has to look inside to find out what it's about. When it turns out to be a sales email they feel they've been had, and your email starts with them already a bit annoyed.

Putting their business name or suburb in the subject is fine and it shows the email was written for them. Just check you've spelled it the way they do, because a mistake in the first five words is hard to recover from. Our guide on writing a first email to a business covers what goes in the email itself.

Why a misleading subject line is a real problem

Plenty of owners assume the Spam Act 2003 has a rule about subject lines. It doesn't have a separate one, but two parts of it still matter here. Section 6 decides whether a message is commercial by looking at its content and the way it is presented, so a sales email with "Checking in" as its subject is still a sales email that needs consent, your details and an unsubscribe. Section 17 requires every commercial message to clearly and accurately identify who authorised it, and a sender name that hides who you are works against that. Our guide on whether cold emailing is legal in Australia covers the rest of the Act.

The rule that does reach subject lines is section 18 of the Australian Consumer Law, which is Schedule 2 of the Competition and Consumer Act 2010. It says a person must not, in trade or commerce, engage in conduct that is misleading or deceptive or is likely to mislead or deceive. The section talks about a person and not just about consumers, so an email from one business to another is covered. The ACCC's guidance says it makes no difference whether a business intends to mislead, that the rule applies to any communication by a business, and that businesses should check the overall impression they give is accurate. It also says a business shouldn't impersonate or pretend to be a different business.

Subject lines that give a false impression are easy to write without thinking:

• "Your quote request" or "About your enquiry" when they never asked for anything.
• "Following up our call" when there was no call.
• "Invoice attached" or "Account update" on what is really a sales email.
• "Notice for your property", worded to look as if it came from the council or the body corporate.
• "Last chance" or "Price ends Friday" when nothing is ending.

Whether any one of these would actually break the law depends on the facts, and this is general information rather than legal advice. Each one does start the relationship with something untrue, though, and the person you were hoping to work with is the first to notice.

Why "Re:" or "Fwd:" on a first email is a bad idea

A "Re:" tells the reader they're looking at a reply to something they wrote, and "Fwd:" tells them someone has passed this on to them. On a first email neither is true, and it's an old enough trick that most people have seen it before. The reader goes looking in their memory for the conversation, doesn't find it and then works out why it's there.

Google's sender guidelines name it directly: they ask senders not to start a subject with "Re:" or "Fwd:" unless the message is an actual reply or forward. It's also the kind of false impression section 18 of the Consumer Law is concerned with, because the subject claims a conversation that never happened.

"Re:" is perfectly fine on a real reply, and that includes a follow-up sent as a reply to your own first email. Our guide on how to follow up a business email explains when to stay in the thread and when to start a fresh email.

What spam filters react to

Neither Google nor Microsoft publishes a list of words that send an email to junk, so be wary of anyone who sells you one. What their sender guidance does talk about is accuracy and how people respond to your email.

Google's email sender guidelines say the subject, headers, display names and other parts of a message should accurately represent who sent it and what it contains, and shouldn't be misleading. Alongside the point about "Re:" and "Fwd:", they ask senders not to use emojis or other unusual characters to imitate graphics in order to deceive or influence the reader. They also warn that hiding content with HTML or CSS can get a message marked as spam, and they ask for links that are visible and easy to understand.

Microsoft's requirements for senders to Outlook.com, Hotmail and Live addresses list the same habits under transparent mailing practices: use accurate subject lines, avoid deceptive headers and make sure recipients have consented to your messages. Microsoft says it may filter or block senders who don't comply.

The common thread is that filters learn from what people do with your email. A subject that leaves someone feeling tricked is the one they report as spam, and those reports count against the emails you send afterwards. Authentication and how much you send matter as much as the words, and our guide on why business emails go to junk covers both.

A quick check before you send

Read your sender name, subject line and first sentence together, the way they'll sit in the reader's inbox, and ask yourself five questions.

1. Would the reader know what the email is about without opening it?
2. Does the first sentence match what the subject promised?
3. Is every word true, including any "Re:", "Fwd:" or deadline?
4. Does the sender name show your own name and your business?
5. Would you be comfortable saying it out loud to them across their front counter?

If the answer to all five is yes, it's ready to go. If you'd rather not write these yourself, Curlew writes each first email in your business name and you approve it before anything is sent.