Open Rate

By Daniel Glushakov

What Is Open Rate in Email Marketing?

In email marketing, open rate is the percentage of delivered emails that were opened by recipients.

It is one of the most commonly used metrics to measure how well an email campaign performed—especially the effectiveness of your subject line, sender name, and audience targeting.

Open rate formula

Open rate = (Emails opened ÷ Emails delivered) × 100

For example, if you send an email to 10,000 recipients and 9,500 emails are delivered, and 1,900 recipients open it:

Open rate = (1,900 ÷ 9,500) × 100 = 20%

What Open Rate Measures (and What It Doesn’t)

Open rate can be useful, but it has limitations.

It can indicate:

  • How appealing your subject line is
  • Whether your audience recognizes your brand
  • Whether your list is engaged
  • Whether your targeting is relevant

It does not reliably measure:

  • True engagement
  • Content performance
  • Conversions

An open doesn’t mean someone read the email—it only indicates the email was likely displayed.

Why Open Rate Is Less Reliable Today

Open rate tracking depends on a tracking pixel (a small invisible image). An open is recorded when that pixel loads.

However, many email clients now block or pre-load tracking pixels, which makes open rate less accurate.

Common reasons open rates are inflated or inaccurate:

  • Apple Mail Privacy Protection (MPP) pre-loads images, creating false opens
  • Some clients block images by default
  • Some security systems scan emails and trigger opens artificially

Because of this, open rate should be treated as a directional metric—not a precise one.

What Impacts Open Rate?

Several factors influence open rate.

Subject Line

Clear, relevant subject lines usually perform best.

Sender Name

Recipients are more likely to open emails from senders they recognize and trust.

Timing

The day and time you send can affect visibility and engagement.

Audience Quality

A clean, engaged list leads to higher open rates.

Deliverability

If your emails land in spam or promotions, fewer people will open them.

How to Improve Open Rate

  • Segment your list to send more relevant emails
  • Use clear, benefit-driven subject lines
  • Avoid spammy language and clickbait
  • Maintain good list hygiene (remove inactive contacts)
  • Use consistent branding and sender names
  • Test subject lines with A/B testing
  • Ensure your domain is authenticated (SPF, DKIM, DMARC)

Open Rate vs Click Rate

Open rate measures attention.

Click rate measures action.

Because opens are less reliable, many marketers focus more on:

Key Takeaway

Open rate is the percentage of delivered emails that were opened. It helps indicate subject line effectiveness and audience interest, but it’s less reliable than it used to be due to privacy and tracking changes.

For a more complete view of performance, open rate should be analyzed alongside clicks, conversions, and overall engagement.

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