Sender Reputation
A score assigned to your sending domain and IP address by email providers, based on your sending behavior, engagement rates, and complaint history — directly determining whether your emails reach the inbox or spam folder.
Your Sender Reputation Is Your Email Credit Score
Email providers do not evaluate each email individually. They look at your track record. If your domain has a history of high engagement, low bounces, and few spam complaints, your emails get the benefit of the doubt — inbox placement. If your history shows spam complaints, high bounce rates, and low engagement, everything you send gets scrutinized and filtered.
This is why a single bad campaign can haunt you for weeks. One blast to a purchased list with a 15% bounce rate and 2% spam complaint rate does not just tank that campaign — it tanks every campaign you send afterward until your reputation recovers.
How Sender Reputation Is Calculated
| Factor | Weight | How to Optimize |
|---|---|---|
| Spam complaints | Very high | Keep below 0.1% per send |
| Bounce rate | High | Keep below 2%, clean list quarterly |
| Engagement rate | High | Send to engaged contacts, segment list |
| Sending consistency | Medium | Maintain steady volume, avoid spikes |
| Spam trap hits | Very high | Never buy lists, verify addresses |
| Authentication | Medium | Implement SPF, DKIM, DMARC |
Your reputation is tracked at both the domain level and the IP level. If you use a shared IP (common with email marketing platforms), other senders on that IP affect your deliverability. Dedicated IPs give you full control but require sufficient volume (50K+ emails/month) to maintain a stable reputation.
Protecting Your Sender Reputation
Separate your sending streams. Use your primary domain for transactional and customer emails. Use a subdomain for marketing campaigns. Use a different subdomain for cold outbound. This way, if outbound activity triggers spam filters, it does not affect your customer communication. Monitor your reputation weekly through Google Postmaster Tools. If you see a drop from High to Medium, immediately reduce volume and audit recent campaigns for issues. Prevention is 10x easier than repair.
Frequently Asked Questions
How do you check your sender reputation?
Google Postmaster Tools shows your domain reputation with Gmail (rated High, Medium, Low, Bad). Microsoft SNDS shows your IP reputation with Outlook/Hotmail. SenderScore.org rates your IP on a 0-100 scale. Check all three monthly — your reputation can differ across providers. A domain rated 'High' on Google but 'Low' on Microsoft means your Microsoft deliverability is suffering.
How long does it take to rebuild sender reputation?
30-90 days of consistent, clean sending. Start by dramatically reducing volume — send only to your most engaged contacts. Gradually increase volume by 10-20% per week as engagement metrics improve. Remove all hard bounces and complainers. If your domain is severely damaged, consider warming up a new subdomain while maintaining authentication on your primary domain.
