Every email
after they bought
is a withdrawal.

It's how you hit this quarter's number. Every send past the fatigue threshold pulls demand forward and trades long-term goodwill for short-term clicks. The detractors you create today were going to be repeat customers next year.

Open rate measures what gets opened — not what gets resented. Apple Mail Privacy Protection pre-loads mail and registers opens nobody made, and AI inbox summaries in Gmail and Apple Mail now read your email for the customer. The honest signals are unsubscribe rate, spam-complaint rate, and the slow drift of organic repeat-purchase rate. All three move silently before opens do.

Depends on category and consented purpose. As a starting point: 1–3 sends/week for retail and DTC, 1–2/week for B2B SaaS, lower for considered purchases. The hard floor is set by the mailbox providers now: keep spam complaints under 0.1%, and never touch 0.3%. Beyond that, the right answer is the one your audience tells you — through unsubscribes, complaints, and direct preference centers. If you don't have a working preference center, you don't have a frequency strategy. You have a guess.

They're conversion design with the brand cost externalized. The unsubscribe maze you ship hits the funnel of the next campaign too, because the user remembers. Regulators have noticed: an FTC-led review of 642 subscription sites and apps found possible dark patterns on 76% of them, California's privacy regulator fined Honda and Todd Snyder in 2025 over lopsided cookie banners, and EU consumer authorities keep running sweeps. The FTC's click-to-cancel rule was struck down on procedure in 2025 — the agency reopened rulemaking in 2026, and existing law still applies in the meantime.

A/B tests measure the next click. They don't measure the customer who closes the tab and tells two friends. They don't measure the spam complaint that quietly degrades your sender reputation across the whole list. The instruments most marketers run with are blind to the damage they're measuring against.

It makes it worse for over-senders. Gmail's Gemini summaries and Apple Intelligence now condense email before a human reads it, and Gmail, Yahoo and Outlook enforce one-click unsubscribe and complaint-rate limits on bulk senders. Sending more no longer buys more attention. It gets you summarized, deprioritized, or filtered — and the brands people actually trust are the ones that get read.

Pull the calculator above against your real list size and frequency. Pair it with your last 12 months of unsubscribe rate, complaint rate, and repeat-purchase trend. If any of those are drifting the wrong way, the over-marketing tax is already being paid — you just haven't attributed it yet.