Definition
A topic line is the phrase shown in inbox previews, sometimes distinct from the subject, summarising the email. It influences the open decision.
Keep it concise and benefit-led.
The topic line is what recipients see before they open, making it a core open driver. It should complement the subject and front-load value. Testing it with real recipients reveals what resonates.
Writing Topic Lines
Keep it concise and benefit-led.
Align it with the subject and preview text.
Why It Matters
The topic line is what recipients see before they open, making it a core open driver. Understanding it improves your most visible copy.
Best Practices
- Keep it concise and benefit-led.
- Align it with the subject and preview text.
- Test it with real recipients.
- Front-load the value.
- Avoid repeating the subject.
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Related Glossary Terms
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Abandoned Cart Email
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AI Content Detection
AI content detection refers to the growing ability of email clients, spam filters and consumers to identify machine-generated email copy. It matters for deliverability, trust and engagement in an era of mass-produced AI marketing email.
AI Email Summary
An AI email summary is a short, machine-generated overview of an email's key points, shown by Gmail, Outlook and Apple Mail before a recipient opens the message. It is reshaping how email marketers think about subject lines, preview text and open rates.
AI-Generated Content in Email
AI-generated content in email is copy, images, code or subject lines produced by artificial intelligence tools to speed up campaign production and testing.
AI Inbox Summary
An AI inbox summary is an AI-generated digest that condenses unread email — often highlighting news, actions and senders — changing how clearly your marketing email reaches and engages subscribers.
Frequently Asked Questions
The summary line shown in inbox previews, often near the subject. The topic line is what recipients see before they open, making it a core open driver.
Sometimes platforms display them together or interchangeably. It should complement the subject and front-load value.
It is a key driver of the open decision. Testing it with real recipients reveals what resonates.
Short and to the point. The topic line is what recipients see before they open, making it a core open driver.
It should complement it. It should complement the subject and front-load value.