Everybody knows sending too many emails is bad. Almost nobody has done the math on how bad.
Here’s the math. Three steps, each with a specific output. By the end you’ll have a dollar figure representing the revenue your email program destroys by sending more than your contacts want.
Fair warning: the number will be imprecise. Several calculations require assumptions, which I’ll flag. But an imprecise number is infinitely better than no number — which is what most teams are working with.
Step 1: Find Your Fatigue Threshold
If you’re using Motiva, the Frequency Reporting dashboard helps you quickly find your fatigue threshold. You don’t have to build this analysis from scratch.
Otherwise, pull your contactable database from the last ninety days. Group contacts by emails received per month:
For each cohort, calculate unsubscribe rate, hard bounce rate, click-through rate, and conversion rate — all per email sent. Plot them on the same chart.
In most databases, engagement per email declines as frequency increases, but not linearly. There’s a point where the decline steepens. That’s your fatigue threshold.
A wrinkle: correlation isn’t causation here. Maybe your high-frequency cohort unsubscribes because the content is bad, not because there’s too much of it. If your high-frequency sends are also your worst sends, frequency isn’t the real problem. Find the threshold anyway. Even an approximate one moves the conversation forward.
Step 2: Price the Contacts You're Losing
Every unsubscribe permanently removes a contact from your addressable audience. Marketers rarely put a dollar value on this. You should.
Email-attributed revenue per contact per year = Total email-driven revenue ÷ contactable database size.
If your program generates $2M from 100,000 contacts, each is worth ~$20/year. Average contactable lifespan of three years puts lifetime value at $60.
Annual attrition from over-mailing: Take your Saturated cohort. A 2% unsubscribe rate per send at 12 emails/month is roughly 24% annual attrition from unsubscribes alone.
If that cohort contains 20,000 contacts: 4,800 contacts × $60 = $288,000/year in lifetime value destroyed from one frequency band.
Now — not all of those contacts would have converted. The $60 LTV is an average across the whole database, including contacts who never would have bought. The true loss is somewhere between this number and zero. But even at half this estimate, it’s significant. The attrition is real regardless of how you value it.
Run the same calculation for every cohort above the fatigue threshold.
Step 3: Measure What the Extra Sends Actually Earn
Now the other side. What revenue do the above-threshold emails actually produce?
If your threshold is six emails/month and you’re sending twelve, isolate the performance of sends seven through twelve. In most databases, CTR and conversion rates in the over-frequency zone are dramatically lower.
But “most databases” isn’t yours. If your over-threshold emails generate meaningful revenue, the calculus changes. Maybe your audience is unusually tolerant. The point of the audit is to know, not to assume.
The Frequency Tax
Frequency tax = (attrition cost + deliverability drag) − marginal revenue from excess sends.
Using our example numbers: attrition cost $288K and marginal revenue $40K. Estimated frequency tax: somewhere between $200K to $300K/year.
That range is wide. It should be — these are estimates with real uncertainty. But even the low end makes frequency a P&L conversation, not a preferences debate.
What to Do With the Number
Reframe the executive conversation. Stop arguing about what “feels right” or what “best practice” says. Show the marginal cost vs. marginal return for each additional send. CFOs get this framing instantly. It’s their language.
Set per-contact frequency caps that flex. Not a blanket cap. Active engagers tolerate more. Contacts showing early fatigue — declining opens, fewer clicks, longer time-to-open — receive less. Total volume may stay flat or increase, because you reclaim capacity wasted on over-mailed contacts.
This is what Motiva’s Frequency Management does: multiple frequency caps with automatic priority enforcement when multiple campaigns compete for the same contacts. It handles the “who gets what and when” decisions that are impossible to manage manually across teams with shared audiences.
The spreadsheet audit takes a morning using Motiva’s Frequency Report. Three exports from your MAP: send volume per contact (90 days), engagement metrics per frequency cohort, unsub and bounce rates per cohort. The math is arithmetic. The conversation it starts is strategic — and for most organizations, it’s the first time anyone has framed email frequency as a financial question with a specific dollar answer.
Learn more about Frequency Management by reading Many Teams, Shared Contacts: How to Control Email Volume with Frequency Management and The Big, Burning Questions about Frequency Management – Answered.
