What can I do to reduce unknown user rate now?
- Review your infrastructure to make sure you are suppressing unknown users correctly and promptly.
- Establish hard and soft bounce rules appropriate to your sending practices. Remove unknown users on the first 5xx bounce when it contains statements such as "email address does not exist" or "unknown user" in the description. Be sure you do not remove 5xx bounce emails when caused by "spam violations", "spam policies", etc
How do I prevent future unknown users?
- Sending a "Welcome" or "Confirmation" message from a separate IP space allows for bounce processing of invalid addresses and ensures that high unknown user rates for new subscribers do not impact performance of regular email campaigns sent from different IPs.
- On sign-up pages, ask customers to type in the email address twice to prevent "fat fingering" mistakes which could unintentionally result in an address that does not exist.
- When receiving subscriptions from third party partners, affiliates, or list services:
- Test a sample of the file from a separate IP space and monitor unknown user rates before adding the file to the database.
- Review the partner data file to ensure that malformed, role account and nonsensical email addresses are removed.
- Mail partners data from separate IP space to monitor their on-going data quality and Unknown User rates.
- Regularly audit partner's sign-up process to ensure that it meets industry best practices for address collection.
- Establish an on-going process for actively removing subscribers that are both old and inactive.
