How to Write Subject Lines That Get One-to-One Emails Opened

Most subject line advice comes from newsletter marketing: curiosity, emojis, urgency. For an email sent to one person who knows you, the opposite works. Here is what gets one-to-one business emails opened, and how to check it on your own emails.

Table of contents

Be specific, not clever

"Q4 proposal for Northwind, 3 options" beats "Quick question" every time. The recipient should know what is inside and why it matters to them before opening.

Name the next step

When you need something, say it: "Signature needed for the March contract" or "Two dates for our kick-off call". It is easier to act on, and easier to find later.

Keep it short

Mobile inboxes cut subject lines after about 30 to 40 characters. Put the important words first.

What to avoid

• Generic subjects: "Follow-up", "Checking in", "Hello".
• Fake replies: "Re:" on an email that is not a reply erodes trust.
• Capitals and exclamation marks, which also look like spam to filters.

Measure on your own emails

Open tracking lets you compare. Note which subjects get opened within hours and which wait days. After a dozen emails, your own patterns are clearer than any generic rule. What a good open rate looks like is in what is a good open rate for one-to-one email.

Conclusion

For one-to-one email, the best subject line is the most useful one: specific, short and clear about what you need. Then let your open data tell you what works for your contacts.

Frequently asked questions

Should I personalise the subject with the name?

It helps less than being specific. The company name or the project name usually works better than the first name.

Do emojis help?

Rarely in business email. They can look like marketing and some filters treat them as a spam signal.

Does the subject line affect deliverability?

Yes, spammy wording can push an email to spam; see our article on how to tell if your email went to spam.

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