Preview text sits right next to your subject line in the inbox, and most teams still treat it as an accident rather than a decision. GetResponse benchmark data puts the average open rate for emails with a custom preview line at 44.67%, against 39.28% for emails without one, a gap of more than five points that comes from nothing more than writing one extra sentence with intent.

What preview text actually is, and what it is not

Preview text, also called a preheader, is the short snippet an inbox pulls in next to or below your subject line. Left unset, most inboxes grab whatever text appears first in the email's code, which is often unsubscribe boilerplate or a stray line of alt text. Roughly a quarter of subscribers read the preview line before deciding whether to open at all, which makes it a second headline rather than decoration.

It is worth being precise about what preview text does not do. It has no bearing on whether your email reaches the inbox or the spam folder, that outcome is decided by authentication and sender reputation, covered in our SPF, DKIM, and DMARC guide. What it does influence is whether, once your email has landed, someone actually opens it.

The character counts that matter

Different clients cut preview text off at different lengths, and writing past the shortest limit wastes your best line on people who will never see it. Outlook typically shows somewhere between 35 and 55 characters, Gmail on mobile shows roughly 40 to 90, and Apple Mail can stretch up to around 140. The practical rule: put your most important message in the first 40 to 50 characters, and treat anything past 140 as invisible to every major client.

IMPORTANT

Front-load the value. If your preview text only starts getting interesting after 60 characters, most subscribers on Outlook or Gmail mobile will never read that part.

What a good preview line actually does

• Sharpens the subject line rather than repeating it. If your subject line asks a question, the preview line can hint at the answer, not restate the question.
• Adds a detail the subject line did not have room for, a number, a name, or a specific benefit.
• Reads like a natural continuation of the subject line, so the two work as one unit rather than two disconnected fragments.

Litmus benchmark findings, summarised by DailyStory, found that customised preview text lifted open rates by 10 to 20% in B2B campaigns specifically, with action-oriented preview copy showing a further engagement lift when the subject line, sender name, and preview worked together as a single unit rather than three separate afterthoughts.

A word on measuring the win

Open rate itself carries the usual asterisk since Apple's Mail Privacy Protection began pre-loading messages in 2021, so treat any open rate lift from preview text as directional rather than exact. What holds up more reliably across clients is click-to-open rate, since a click still requires a genuine human action. If a stronger preview line is doing its job, that number should move too, not just the open count.

Mail Blaze's email builder shows a live preview of exactly how your subject line and preheader will render across the major clients before you send, so you are never guessing at where the cut-off falls.

Frequently asked questions

Does preview text affect deliverability?

No. Preview text has no direct effect on whether an email reaches the inbox or the spam folder. That outcome depends on authentication and sender reputation. A clear preview line can, however, reduce the chance a recipient marks an already-opened email as spam, which indirectly protects reputation over time.

How long should preview text be?

Aim for 80 to 130 characters in total, with the essential message inside the first 40 to 50 characters, since that is the range every major client reliably displays before truncating.

What should I avoid in preview text?

Avoid letting it default to generic boilerplate like 'view this email in your browser', and avoid simply repeating the subject line word for word. Both waste the second impression a subscriber gets before opening.

Does preview text still matter if Apple pre-loads my emails?

Yes. MPP affects open tracking, not what a human actually sees in their inbox. The 35 to 55% of opens that happen outside Apple Mail still rely on preview text to decide whether to open, and a strong preview line continues to support clicks and replies regardless of how opens are measured.

Mail Blaze is an email marketing platform specialising in email engagement, built around the idea that the small, unglamorous decisions in an email programme usually carry more weight than the flashy ones.

Preview your next subject line and preheader together in Mail Blaze's email builder before you send.

P.S. If you're not sure whether your current preview text is helping or hurting, forward us your last send. We read these seven days a week.

Where to add your preheader in Mail Blaze?

When creating a campaign, go to the SETUP section, click VIEW ADVANCED SETTINGS, and enter your PREHEADER text there.