Why email frequency impacts open rates and revenue differently

Email frequency increased from twice weekly to daily. Open rate dropped from 28% to 19%. The marketing team worried—engagement was declining. But revenue from email grew 34%. More emails at lower open rates produced more total revenue than fewer emails at higher open rates. The efficiency metric suggested problems while the outcome metric showed success. Open rates and revenue don’t move together.

Email frequency affects per-email engagement and total program output through different mechanisms. Understanding why these metrics diverge helps you optimize for business results rather than engagement metrics that might mislead.

Why higher frequency lowers open rates

Per-email engagement declines with volume:

Inbox fatigue reduces individual email attention

Subscribers who receive daily emails can’t open every one. They selectively engage with emails that catch their attention at the right moment. More emails means more competition for limited attention. Each individual email gets less consideration.

Novelty decreases

Weekly emails feel like events. Daily emails become routine. The excitement of “new email from brand X” diminishes when emails arrive constantly. Reduced novelty means reduced urgency to open.

Content quality often drops with volume

Producing compelling content daily is harder than weekly. Higher frequency can mean more filler, more repetition, more “just sending something.” Lower content quality earns lower open rates.

Subject line fatigue

Finding fresh, compelling subject lines daily is difficult. Subscribers learn to pattern-match and ignore familiar approaches. Subject line effectiveness declines as the same writer sends more frequently.

Unsubscribes and disengagement increase

High frequency pushes some subscribers to unsubscribe or mentally tune out. The remaining list includes more passive subscribers who rarely open but haven’t bothered unsubscribing. List quality shifts toward less engaged subscribers.

Why higher frequency increases revenue

Total revenue can grow despite lower per-email engagement:

More emails means more total opens

Two emails weekly at 28% open rate = 0.56 opens per subscriber per week

Seven emails weekly at 19% open rate = 1.33 opens per subscriber per week

Despite lower rate, daily emails generate 138% more total opens. More opportunities to drive revenue even at lower per-email engagement.

More moments capture purchase intent

A subscriber ready to buy might not be ready on Tuesday when your weekly email arrives. Daily emails increase the chance of reaching subscribers when they’re in buying mode. Frequency captures more purchase-ready moments.

Top-of-mind presence drives direct visits

Even unopened emails keep your brand visible in inbox. When subscribers decide to shop, they remember you. Frequent presence creates mental availability that drives visits even without email clicks. This revenue doesn’t attribute to email opens but results from email presence.

Different subscribers respond to different emails

Subscriber A opens promotional emails. Subscriber B opens new arrival emails. Subscriber C opens content emails. More emails means more chances to match content to subscriber preference. Variety increases total response across diverse audience.

Urgency and scarcity require frequency

Time-sensitive promotions, flash sales, and limited availability need timely communication. Infrequent senders miss urgency windows. Frequent senders can communicate time-sensitive opportunities when they arise.

The math of frequency trade-offs

Calculate the actual trade-off:

Scenario: 50,000 subscribers

Low frequency (2x/week):

8 emails/month × 28% open rate = 112,000 total opens

5% click rate on opens = 5,600 clicks

8% conversion on clicks = 448 conversions

$75 AOV = $33,600 monthly email revenue

High frequency (daily):

30 emails/month × 19% open rate = 285,000 total opens

4% click rate on opens = 11,400 clicks

6% conversion on clicks = 684 conversions

$72 AOV = $49,248 monthly email revenue

Despite lower open rate, click rate, conversion rate, AND AOV, high frequency produces 47% more revenue. Volume overwhelms efficiency decline.

When frequency hurts revenue

The math doesn’t always favor more emails:

List destruction exceeds volume gains

If high frequency causes mass unsubscribes, the shrinking list can’t sustain revenue growth. Losing 20% of subscribers to gain 10% more revenue per remaining subscriber is a bad trade. Monitor list health alongside revenue.

Deliverability damage

Very high frequency with low engagement signals spam to email providers. Declining deliverability means fewer emails reach inbox at all. Deliverability problems can eliminate frequency benefits entirely.

Brand perception damage

Excessive frequency can annoy customers and damage brand relationship. Revenue might grow short-term while long-term customer lifetime value suffers. Brand damage is hard to measure but real.

Content quality collapse

If frequency increase comes with severe content quality decline, engagement might drop more than volume increases. Ten bad emails might perform worse than two good emails despite the volume difference.

Finding optimal frequency

Balance volume and efficiency:

Test incrementally

Increase frequency gradually and monitor total revenue, not just open rates. If revenue grows, continue increasing. If revenue plateaus or declines, you’ve found your limit.

Segment frequency by engagement

Active subscribers might tolerate daily emails. Inactive subscribers might need weekly at most. Sending different frequencies to different segments optimizes both engagement and revenue.

Monitor unsubscribe rate

Rising unsubscribes signal frequency exceeding subscriber tolerance. Acceptable unsubscribe rates depend on acquisition rate and lifetime value, but acceleration indicates problems.

Watch deliverability metrics

Inbox placement, spam complaints, and bounce rates reveal whether frequency is damaging email health. Deliverability decline undermines all other frequency benefits.

Consider content sustainability

Can your team produce quality content at the planned frequency? Unsustainable frequency leads to content quality decline that eventually hurts results.

Reporting email performance accurately

Use the right metrics for the right purposes:

Open rate: Measures per-email engagement. Useful for comparing subject lines, send times, and content approaches. Not useful for evaluating frequency strategy.

Total revenue: Measures program output. Useful for evaluating frequency strategy and overall email contribution. The metric that matters for business decisions.

Revenue per email sent: Measures efficiency. Helps understand whether frequency is productive or just busy. Declining revenue per email suggests diminishing returns.

Revenue per subscriber: Measures list productivity. Growing revenue per subscriber indicates healthy program. Declining might signal list fatigue.

Frequently asked questions

Is it ever right to optimize for open rate?

Yes, when testing content and tactics within a fixed frequency. Better subject lines, better send times, and better content should improve open rates. But sacrificing revenue for open rate improvement is usually wrong.

How do I know if I’m emailing too much?

Watch for accelerating unsubscribes, declining deliverability, and revenue per email dropping faster than volume increases. These signals indicate frequency exceeding optimal levels.

What’s the right email frequency?

Varies by industry, audience, and content quality. Some audiences tolerate daily emails; others prefer weekly. Test your specific situation rather than following generic benchmarks.

Should I worry about low open rates?

Only if they indicate problems like deliverability issues, list quality decline, or content problems. Low open rates from high frequency that produces more revenue are acceptable. Low open rates from poor execution need fixing.