Your sender reputation is your email program's credit score. It decides whether Gmail, Outlook, and Yahoo deliver your messages to the inbox, spam, or not at all. A strong reputation = reliable inbox placement. A damaged one = even good campaigns disappear into spam.
Email sender reputation is a score assigned to your sending domain and IP address by ISPs and email providers. Every time you send, the receiving mail server checks it and decides:
Reputation is calculated at two levels: domain reputation (tied to yourcompany.com) and IP reputation (tied to your sending IP address).
| Negative signals | Impact |
|---|---|
| High bounce rate (> 2%) | 🔴 High |
| Spam complaints (> 0.1%) | 🔴 High |
| Spam trap hits | 🔴 Very high |
| Blacklist listings | 🔴 Very high |
| Sudden volume spikes | 🟠 Moderate |
| Low engagement | 🟡 Moderate |
| Positive signals | Impact |
|---|---|
| Low bounce rate (< 2%) | 🟢 Strong |
| Low spam complaints (< 0.08%) | 🟢 Strong |
| High open & click rates | 🟢 Strong |
| Consistent sending volume | 🟢 Moderate |
| Proper SPF / DKIM / DMARC | 🟢 Strong |
| "Not Spam" markings from users | 🟢 Strong |
Free. Shows domain reputation (High, Medium, Low, Bad) for Gmail delivery. Essential for anyone sending to Gmail or Google Workspace. → postmaster.google.com
IP reputation score from 0–100. Above 80 is healthy; below 70 means deliverability problems are likely. → senderscore.org
Checks your domain and IP against 100+ major blacklists. → mxtoolbox.com/blacklists
Microsoft's equivalent of Postmaster — IP reputation for Outlook/Hotmail. → sendersupport.olc.protection.outlook.com/snds
| Domain reputation | IP reputation | |
|---|---|---|
| Tied to | Your sending domain | Your sending IP |
| Moves with you? | ✅ Yes — permanent | ❌ No — stays with IP |
| Affected by shared sending? | ❌ No | ✅ Yes (shared IPs) |
| More important today? | ✅ Primary signal | Less so |
Gmail and modern ISPs have shifted toward domain reputation as the primary signal. Using a new IP doesn't reset your reputation — your domain carries the history.
Four signals do the bulk of the damage. Understanding each is the difference between protecting your reputation and accidentally torpedoing it.
Sending to invalid addresses tells ISPs you didn't verify your list — a classic spam behavior. A single campaign with 10%+ bounce rate can cause a significant reputation drop that takes weeks to recover from. Fix: Verify your list with KillBounce before every campaign. Target bounce rate under 2%.
Every time a recipient clicks "Mark as spam", it's a vote against your reputation. Gmail's spam complaint threshold is 0.1% — above that, Gmail starts filtering your emails automatically. Above 0.3%, your emails may be rejected entirely. Fix: Only send to opted-in contacts. Provide an obvious unsubscribe link. Honor unsubscribes within 24 hours.
Spam traps are email addresses that should never receive legitimate mail — either never-valid addresses or abandoned addresses recycled by ISPs and blacklist providers. Hitting them signals serious list hygiene problems. Fix: Never buy lists. Verify existing lists with KillBounce. Remove subscribers who haven't engaged in 6–12 months — abandoned mailboxes are the most common source of traps.
Jumping from 1,000 emails/day to 100,000 overnight triggers ISP scrutiny — that's the pattern of a compromised account or a spammer ramping up. Fix: Always ramp volume gradually. Double sends every 3–5 days during warm-up. Once warmed up, keep daily volume consistent within a 30% band.
Reputation repair takes time — there's no instant fix. But here's the fastest path:
Containment first. Continuing the bleeding makes recovery longer.
Remove invalids, disposables, role-based, and unengaged contacts. This is the single highest-leverage step.
Identify segments with high complaint history. Remove them. If a list source produced disproportionate complaints, stop importing from that source.
Confirm SPF, DKIM, and DMARC are correctly configured. Use mxtoolbox.com to test. Missing or broken authentication amplifies every other reputation problem.
Start with your most engaged 10% of contacts — people who opened or clicked in the last 30 days. Their engagement signals will start rebuilding your reputation.
Double volume every week as reputation metrics improve. Watch bounce rate, complaint rate, and Postmaster Tools data — any regression means slow down further.
Track reputation changes in real-time. Expect 4–8 weeks for meaningful recovery if you stay disciplined.
The best strategy is to never let your reputation drop in the first place. The discipline that prevents damage is much cheaper than the recovery that fixes it:
For a brand new domain, expect 4–6 weeks of careful low-volume sending before you have a meaningful reputation. Don't rush the warm-up phase.
Your domain reputation stays with your domain regardless of which ESP you use. IP reputation resets if you move to a new IP, but domain is what matters most today.
A single very bad campaign (very high bounce rate, mass spam complaints) can cause significant damage. This is why list quality is so critical before every send.
No. Domain authority is an SEO metric for search rankings. Sender reputation is specific to email deliverability. Completely separate systems.
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