Definition
Sender Score is a numerical reputation ranking from 0 to 100 that measures how trustworthy an email sender appears to mailbox providers. It is calculated by Validity using data from their network of mailbox provider partnerships, feedback loops, and panel data. A high Sender Score means your emails are likely to reach the inbox. A low score means they will probably be filtered to spam or blocked.
Sender Score is the industry standard for sender reputation measurement. Most major mailbox providers and email service providers reference Sender Score data when making deliverability decisions.
Formula
Sender Score is calculated using a weighted algorithm that considers several factors:
Sender Score = weighted composite of complaint rate, unknown user rate, spam trap hits, and engagement
| Factor | Weight | Target Threshold |
|---|---|---|
| Spam complaint rate | 30-40% | Below 0.1% |
| Unknown user rate | 20-25% | Below 3% |
| Spam trap hits | 20-25% | Zero |
| Engagement rate | 10-15% | Above 15% |
| Volume consistency | 5-10% | Steady sending pattern |
Average Benchmarks
| Score Range | Classification | Inbox Placement Rate |
|---|---|---|
| 90-100 | Excellent | 95-99% |
| 80-89 | Good | 85-95% |
| 70-79 | Fair | 70-85% |
| 50-69 | Poor | 40-70% |
| Below 50 | Critical | Under 40% |
Most legitimate senders maintain a score above 80. Anything below 70 requires immediate action.
How to Improve Your Sender Score
- Reduce spam complaints: Use confirmed opt-in, make unsubscribe easy, and target engaged subscribers only. Keep complaint rates below 0.1%.
- Eliminate spam trap hits: Remove inactive subscribers regularly. Validate emails at point of capture. Never purchase email lists.
- Lower bounce rates: Remove hard bounces immediately. Suppress soft bounces after three attempts. Use email verification services.
- Increase engagement: Send relevant content to segmented audiences. Remove subscribers who have not opened or clicked in 90 days.
- Maintain consistent volume: Avoid sudden spikes or drops in sending volume. Ramp up gradually when adding new subscribers.
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Frequently Asked Questions
Sender Score is a specific product from Validity. Sender reputation is the broader concept that every mailbox provider calculates independently. Sender Score provides a single number that correlates highly with how major providers treat your mail, but it is not the only score that matters.
You can check your Sender Score for free at senderscore.org by entering your sending IP address or domain. Google Postmaster Tools provides Gmail-specific reputation data. Microsoft SNDS provides Outlook.com reputation data.
Sender Score is updated daily based on rolling data from the previous 30 days. This means a single bad day has limited impact on your score, but consistently poor performance will gradually lower your score over several weeks.
Common causes include a high complaint campaign, sending to an old list with many spam traps, a data breach that results in unauthorised email being sent from your domain, or a sudden increase in sending volume without proper warm-up.
Yes. Stop sending to problematic segments immediately. Clean your list thoroughly. Reduce volume until complaint and bounce rates stabilise. Maintain consistent sending to engaged subscribers for 4-12 weeks. Most senders see measurable improvement within 30 days of clean sending practices.