Open Rate
The percentage of delivered emails that were opened by recipients.
Definition
Open rate measures the percentage of email recipients who opened your email out of the total number of delivered emails. It is calculated by dividing the number of unique opens by the number of delivered emails and multiplying by 100. Open rate is a fundamental engagement metric that indicates initial interest in your emails. The formula is: (Unique Opens / Emails Delivered) x 100.
Why It Matters
Open rate helps you understand if your subject lines and sender name are compelling enough to get recipients to open. It is an early indicator of campaign health and can signal problems with deliverability, timing, or relevance. However, open tracking has become less reliable since Apple Mail Privacy Protection launched in 2021, which pre-fetches tracking pixels.
How It Works
Open tracking works by embedding an invisible 1x1 pixel image in the email. When the recipient opens the email and images load, the pixel is requested from a server, registering an open. This logs the timestamp, device type, and sometimes location. However, this method has limitations: some email clients block images, and Apple's privacy features pre-fetch images without the user actually opening.
Example
You send a newsletter to 10,000 subscribers. 9,800 are delivered (200 bounced). Of those, 2,450 unique recipients open the email.
Your open rate is: 2,450 / 9,800 x 100 = 25%
The following week, you try a different subject line and get 2,940 opens - a 30% open rate. You learn that personalized subject lines with the recipient's name perform 20% better for your audience.
Note: About 45% of your opens may be from Apple Mail users, which could be inflated by Mail Privacy Protection.
Best Practices
- 1Write compelling, relevant subject lines that create curiosity or state clear value
- 2Use a recognizable sender name that recipients trust
- 3Test different send times to find when your audience is most active
- 4Segment your list to send more relevant content to each group
- 5Consider click rate as a more reliable engagement metric post-Apple MPP
- 6A/B test subject lines systematically to improve over time
Advanced Analytics
Sequenzy provides detailed open rate tracking with Apple MPP detection to give you accurate engagement insights.
Learn MoreOpen Rate Formula Table
| Metric | Formula | Use |
|---|---|---|
| Unique open rate | Unique opens / delivered emails | Standard campaign open metric |
| Total opens | All opens including repeat opens | Interest depth and repeated viewing |
| Open-to-click context | Clicks / opens | Body effectiveness among openers |
| Delivered base | Sent minus bounces | Correct denominator for open rate |
Open Rate Diagnostic Table
| Pattern | Likely cause | Next test |
|---|---|---|
| Low opens, normal clicks among openers | Inbox preview or send timing issue | Subject, sender, and preheader |
| High opens, low clicks | Body content or CTA mismatch | Offer clarity and email layout |
| Sudden open spike | Apple MPP or bot prefetch | Compare clicks and MPP share |
| Provider-specific open drop | Tracking, engagement, or placement change | Review provider-level delivery and engagement data |
The live test in our Tracking Pixel Generator shows what an Apple MPP prefetch or proxy load looks like next to a real open, which makes these spikes easier to recognize.
Open Rate Improvement Table
| Lever | What to change | Why it helps |
|---|---|---|
| Sender name | Use recognizable brand or person | Builds trust in inbox |
| Subject line | State value or create relevant curiosity | Gives reason to open |
| Preheader | Extend the subject line | Adds context before open |
| Segmentation | Send more relevant campaigns | Relevance improves inbox behavior |