How do ISPs build sender reputation databases?

ISPs build sender reputation databases by continuously collecting and analyzing signals from mail flowing through their systems.

Sending patterns are tracked: volume, consistency, growth rates, and sudden changes. The database learns what normal looks like for each sender.

Complaint rates from user spam reports feed directly into reputation scores. Senders generating complaints see their scores decline.

Bounce rates indicate list quality. High bounces suggest purchased lists or poor hygiene, lowering reputation.

Engagement metrics where tracked show whether recipients want the mail. Opens, clicks, and replies improve reputation. Deletes and ignores harm it.

Spamtrap hits provide definitive evidence of list problems. Hitting monitored traps causes immediate reputation damage.

These signals aggregate over time, creating a comprehensive picture of each sender's trustworthiness.

Your reputation database entry is the sum of your behavior. Every message contributes to the record.