Sender Reputation Check: IP & Domain Reputation Explained
Your sender reputation is the single biggest factor in whether your email reaches the inbox. Here is how providers build that score, how to check it, and how to protect it.
What sender reputation is
Every mailbox provider maintains a reputation score for your sending IP and domain. It is built from engagement signals (opens, clicks, replies), complaint rates, bounce rates, spam trap hits and authentication status. High reputation = inbox. Low reputation = spam or rejection.
How to check your reputation
Google Postmaster Tools — free, shows Gmail-specific domain and IP reputation
Microsoft SNDS — free, shows Outlook IP reputation and complaint data
GlockApps — aggregated view across providers via placement tests and monitoring
Sender Score (Validity) — IP reputation on a 0–100 scale
What hurts reputation
High spam complaint rate (above 0.1%)
Sending to inactive or invalid addresses (bounces)
Spam trap hits
Sudden volume spikes without warmup
Failed authentication (SPF/DKIM/DMARC)
Low engagement (no opens, no clicks)
How to improve reputation
Clean your list regularly (remove bounces and unengaged contacts)
Warm up new domains and IPs gradually
Authenticate everything (SPF + DKIM + DMARC)
Make unsubscribing easy (reduces complaints)
Send relevant content to engaged segments
Monitor with tools like GlockApps and Google Postmaster
Evidence & transparency. Checked against public data: provider postmaster documentation and deliverability best practices. Not independently tested by us: specific reputation scoring algorithms. Reader should verify: your own reputation using the tools listed above. Last reviewed: June 2026.
Frequently asked questions
How long does it take to rebuild sender reputation?
Weeks to months, depending on severity. Consistent good sending behavior over 30–90 days typically shows measurable improvement.
Does sender reputation apply to my domain or IP?
Both. Domain reputation follows you even if you change IPs. IP reputation matters especially on shared infrastructure.