Unsubscribe rate
Percentage of recipients who unsubscribed from a given send — a lagging indicator of list fatigue or audience mismatch.
Unsubscribe rate is the share of recipients who clicked unsubscribe in response to a given email, expressed as a percentage of delivered or opened. Industry benchmarks are 0.1-0.3% per send; rates above 0.5% indicate something is wrong — over-mailing, audience mismatch, or content that doesn't match what the recipient signed up for.
Unsubscribes are not the enemy. An unsubscribe is a recipient telling you clearly: "I no longer want this." Honoring the request — promptly, completely, and without retention pressure — preserves sender reputation and removes a non-engaging address from your list. Compare to spam complaints: an unsubscribe is the cleanest possible outcome for a disengaging recipient.
What unsubscribe rate actually measures is "delta between what recipients expected and what they received." A spike in unsubscribes after a particular send means that send broke the expectation set by previous sends. Common causes: sudden cadence increase, repositioned content (going from tactical to promotional, or vice versa), audience expansion to addresses that didn't actually opt in.