IP Reputation
A trust score assigned by ISPs to a specific sending IP address based on its email sending history and behavior.
IP reputation is a score that ISPs assign to each IP address that sends email. It reflects the historical sending behavior from that IP — including bounce rates, spam complaints, sending volume patterns, and blacklist history. A high IP reputation means emails from that IP are likely to reach the inbox, while a low reputation means they'll be filtered to spam or blocked.
Dedicated vs. shared IPs:
- Dedicated IP: You control the reputation entirely. Best for high-volume senders (100K+ emails/month) who can maintain consistent, clean sending practices.
- Shared IP: Your reputation is pooled with other senders on the same IP. ESPs like SendGrid and Mailchimp manage shared IP pools. Cheaper and easier to maintain, but you're affected by other senders' behavior.
How to monitor and improve IP reputation:
- Use Google Postmaster Tools to see your reputation with Gmail (rated High/Medium/Low/Bad)
- Check Microsoft SNDS for Outlook reputation data
- Monitor Sender Score (scored 0-100) from Validity
- Maintain bounce rates below 2% by verifying your lists with SendSure
- Keep spam complaint rates below 0.1%
- Warm up new IPs gradually before sending at full volume
Related Terms
Sender Reputation
A score assigned by ISPs to your email sending domain/IP that determines whether your emails reach the inbox.
Email Blacklist (RBL)
A database of IP addresses and domains known to send spam, used by ISPs to filter incoming email.
Email Warm-Up
The process of gradually increasing email send volume on a new IP address or domain to build trust with ISPs.
Bounce Rate
The percentage of emails that could not be delivered to the recipient's inbox.
Want to learn more?
Read our in-depth blog posts on email verification and deliverability.