Frequency Cap

A frequency cap is a campaign setting that limits the number of times a specific subscriber will see a particular ad within a defined time window. For example, a frequency cap of 3/30 means each subscriber will see a given ad at most 3 times in any 30-day period. In newsletter advertising with open-time ad serving, frequency caps are applied in real time at open time — when the subscriber opens an email, the ad server checks the subscriber's exposure count before serving. MailAdx uses the subscriber's SHA-256 email hash for frequency tracking, meaning caps work without cookies or persistent identifiers. Frequency caps protect subscriber experience (avoiding ad fatigue) and improve advertiser efficiency (budget not wasted on overexposed readers).