Definition
IP reputation is the assessment that email providers and internet service providers assign to your sending IP address based on your email sending history and practices. It functions like a credit score for email — a good reputation means your emails are likely to reach the inbox, while a poor reputation results in filtering, blocking, or spam folder placement.
Reputation is evaluated at both the IP level and the domain level. For smaller senders using shared IP pools (common with many email service providers), domain reputation often matters more. For dedicated IP senders, IP reputation is the primary factor in inbox placement decisions.
Factors That Affect IP Reputation
| Factor | Impact | Description |
|---|---|---|
| Spam Complaint Rate | Very High | Number of subscribers marking email as spam |
| Bounce Rate | High | Percentage of emails that hard or soft bounce |
| Engagement Rate | High | Opens, clicks, and positive subscriber actions |
| Sending Volume | Medium | Consistency of sending volume over time |
| Unknown User Rate | High | Attempts to send to non-existent addresses |
| Blacklist Presence | Very High | Whether IP appears on known DNS-based blacklists |
| Sending History | Medium | Age of IP and historical sending patterns |
Dedicated vs Shared IP Reputation
| Factor | Dedicated IP | Shared IP |
|---|---|---|
| Reputation Control | Full control — only your behaviour matters | Shared with other senders on the same pool |
| Warm-up Required | Yes — new IPs need gradual volume ramp-up | Not applicable |
| Cost | Higher | Lower |
| Best For | High-volume senders (100k+ per month) | Low-volume senders, beginners |
| Risk | All reputation risk is yours | Other senders' poor practices can affect you |
How to Maintain Good IP Reputation
- Monitor complaint rates: Keep spam complaints below 0.1% of delivered emails
- Remove hard bounces immediately: Never attempt redelivery to known invalid addresses
- Send consistently: Avoid dramatic volume spikes or long pauses followed by large sends
- Engage your list: Send to subscribers who want your emails — remove or re-engage inactive ones
- Authenticate your email: Implement SPF, DKIM, and DMARC to protect against spoofing
- Monitor blacklists: Regularly check your IP against major DNS-based blacklists
- Warm up new IPs: Gradually increase sending volume over 4-8 weeks for new dedicated IPs
How to Check IP Reputation
Tools like SenderScore, Talos Intelligence, MXToolbox, Barracuda Reputation Block List, and Google Postmaster Tools provide IP reputation checks. SenderScore rates IPs from 0-100, with scores above 80 considered good and scores below 70 indicating reputation problems.
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Frequently Asked Questions
Building good IP reputation takes 4-8 weeks of consistent, positive sending behaviour. During this warm-up period, start with low volume to your most engaged subscribers and gradually increase. Recovery from a poor reputation typically takes 2-6 months of consistent best practices.
Yes — this is called a shared IP pool, common with most email service providers. The reputation of a shared IP is affected by all senders on that pool. Your email service provider manages shared IP reputation and will separate senders who damage the pool's reputation.
Emails from blacklisted IPs are blocked or sent to spam by major mail providers. To resolve this, identify the cause (usually spam complaints or a compromised sending account), fix the root issue, request removal from the blacklist, and demonstrate improved sending practices over time.