I'm finding the same limitation. Adding the subscriber email to the dynamic link is NOT an option as it would mean there is personally identifiable information in the link which violates Google Analytics Terms of Service (see below for reference).   Why doesn't Constant Contact just make the contact_id field available for inclusion in Dynamic Links?    -- https://support.google.com/analytics/answer/2795983?hl=en   Analytics customers are prohibited from sending personal information to Google. The Analytics terms of service, which all Analytics customers must adhere to, prohibits sending personally identifiable information (PII) to Analytics (such as names, social security numbers, email addresses, or any similar data), or data that permanently identifies a particular device (such as a mobile phone’s unique device identifier if such an identifier cannot be reset). Learn more about how to avoid sending PII. Your Analytics account could be terminated and your data destroyed if you use any of this information. ... View more