Definition
Sender reputation is the history mailbox providers associate with signals such as a sending domain, DKIM domain, IP address, message stream, or combinations of those identities. It is better understood as a changing set of private receiver models than as one portable score.
Positive history is built through wanted, authenticated, consistent mail. Complaints, unknown users, spam-trap hits, suspicious traffic, erratic volume, and compromised infrastructure can weaken it.
Why it matters
Reputation influences whether providers accept, defer, reject, or filter mail. It also explains why two senders using identical templates and infrastructure can receive different outcomes.
How it works
- 01
Receivers identify the sending IP and authenticated domains.
- 02
They combine recent and historical traffic, complaint, bounce, engagement, and abuse signals.
- 03
Models can evaluate each stream and mailbox relationship differently.
- 04
Reputation changes as new behavior replaces or reinforces prior history.
Common mistakes
- Searching for one global reputation score.
- Believing a new IP or domain erases poor sending practices.
- Mixing transactional and promotional traffic so one stream can damage the other.
- Reacting to normal daily variation instead of sustained receiver-specific trends.
Key takeaways
- Reputation belongs to receivers, not senders.
- Domains, IPs, streams, and recipient relationships all contribute.
- Healthy acquisition and low complaints are the strongest long-term controls.