Definition
Email marginal revenue per send is the additional revenue generated by sending one more email, holding other factors constant. It is the change in total revenue divided by the change in the number of emails sent over that increment. This metric captures the economic principle of diminishing returns: as send volume rises, each additional email typically produces less revenue than the one before.
How It Works
Marginal revenue per send measures what the next email is worth, rather than the average value of all emails so far. This distinction matters because email has a saturation point.
- Incremental thinking — the metric compares revenue at two send volumes to isolate the effect of the additional sends.
- Diminishing returns — beyond a certain frequency, additional sends add little revenue and may even subtract value through fatigue and unsubscribes.
- Optimal frequency — the metric helps identify the send volume at which marginal revenue falls below marginal cost, signalling the profit-maximising point.
This concept is central to email-frequency decisions and to understanding the economics of email-send-frequency strategy.
How to Calculate
Calculate marginal revenue per send in three steps:
- Measure revenue at two volumes — record revenue at a lower send volume and at a higher send volume.
- Find the change — subtract the lower-volume revenue from the higher-volume revenue.
- Divide by the change in sends — divide the revenue change by the difference in emails sent.
Marginal Revenue Per Send = Change in Revenue / Change in Emails Sent
| Variable | Description |
|---|---|
| Change in Revenue | Difference in total revenue between two send volumes |
| Change in Emails Sent | Difference in the number of emails sent |
Example
A brand sends 100,000 emails and generates £20,000. It increases to 120,000 emails and generates £22,500. The change in revenue is £2,500 and the change in sends is 20,000, giving a marginal revenue per send of £0.125. The brand compares this against the cost per send to decide whether the extra volume was profitable.
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Frequently Asked Questions
As send frequency rises, the incremental audience reached is less responsive, and recipients begin to fatigue. Each additional email competes for the same finite attention, so its incremental value falls.
Average revenue per send divides total revenue by total sends, while marginal revenue per send measures the change from the last increment of sends. Marginal analysis reveals the value of the next email, which is what frequency decisions require.
When marginal revenue per send drops below the cost of sending an additional email, further volume reduces profit. This signals that send frequency should be held steady or reduced.
Yes. If additional emails trigger enough unsubscribes, complaints, and fatigue, total revenue can fall as volume rises, producing negative marginal revenue. This is a strong signal to cut back frequency.