Sender reputation is a score that email service providers (Gmail, Outlook, Yahoo) assign to your sending domain and IP address based on your email behavior. It determines whether your emails land in the inbox, spam folder, or get rejected entirely. Think of it as a credit score for your email: it takes time to build, drops quickly when you make mistakes, and recovering from damage requires patience and discipline.
Why It Matters
Your sender reputation is invisible but controls everything. A high reputation means 95%+ inbox placement. A low reputation means 40-60% of your emails go to spam, and your team has no idea because the emails still show as "sent" in their platform. The most common reputation killers are sending to invalid addresses (high bounce rate), hitting spam traps, and getting spam complaints. All three are data quality problems.
How to Protect Sender Reputation
- Verify before sending: Run email verification on your list before every campaign. One bad send can tank your reputation
- Monitor bounce rates: Keep hard bounce rates below 2%. Above 5% triggers ISP penalties
- Watch complaint rates: Keep spam complaints below 0.1%. Above 0.3% and you're in trouble
- Authenticate your domain: Set up SPF, DKIM, and DMARC records to prove your emails are legitimate
- Warm up new domains: Start with small volumes to trusted contacts and gradually increase. Don't blast 50,000 emails from a new domain
Example
A company switches email providers and starts sending from a new domain without warming it up. They send 20,000 emails on day one. ISPs flag the sudden volume, bounce rate hits 8% because the list hasn't been cleaned in months, and inbox placement drops to 35%. It takes 6 weeks of careful, low-volume sending to rebuild the reputation.
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