Sender Reputation Score Calculator

What "sender reputation" actually means in 2026

There is no single "sender score" that all ISPs share. Each major mailbox provider runs its own proprietary reputation scoring, and the signals that feed into one provider's score do not necessarily feed into another's. The composite score this calculator produces is a synthesised approximation across the publicly known signal weights at Gmail, Microsoft, Yahoo, and Apple. It correlates well enough with actual placement to be useful as a self-assessment, but it is not a number any specific ISP would recognise as authoritative.

The 2025-2026 changes to the visible reputation tooling matter here. Google Postmaster Tools v2 launched in September 2025, retiring the Domain Reputation gauge that operators had used for years. The four-tier "Bad / Low / Medium / High" indicator is gone.

The replacement signals are spam rate, compliance status against the Bulk Sender Requirements, and a per-day delivery-error breakdown. Microsoft SNDS still publishes IP-level reputation. Yahoo Sender Hub provides complaint and unsubscribe data. The era of looking at a single Domain Reputation tile is over; reputation now comes from synthesising multiple signals, which is what this calculator approximates.

Per-provider reputation tooling worth checking directly

The calculator gives you a synthesised view; the authoritative view comes from the providers themselves. Each major mailbox provider exposes free reputation tooling, and operators who use this calculator should cross-reference against the provider tools when something looks off. Three minutes per provider per week is the typical operational cadence.

Two notes about reading these tools. First, the data has lag. Postmaster Tools updates spam rate with roughly 24-hour delay; SNDS updates daily; Sender Hub similar. A reputation event that happened today shows in the tools tomorrow.

That delay matters operationally. The calculator's "current state" estimate based on your inputs may be more current than the provider tools when you check them.

Second, the per-provider scores do not always agree. A programme can have healthy Gmail reputation and damaged Microsoft reputation (or vice versa) because the providers weight signals differently. The calculator's composite score averages across providers; the per-provider story is more nuanced.

The asymmetry between damage and recovery

The most important operational fact about reputation is that it is asymmetric. A bad week of metrics can cost you 30-40 points of reputation. Recovering those 30-40 points takes several weeks of consistently good metrics. The calculator's score gives you the current state; the recovery path from a low score is much slower than the path that got you there.

What to do at each score band

85-100: Excellent

Top decile. Continue current practices, monitor for drift. The risk at this level is complacency — programmes that stay healthy for years often fail to notice early-warning signals because everything looks fine on the dashboard. Set up alerts for any single metric crossing a threshold (complaint rate above 0.05%, bounce rate above 0.5%, blocklist presence anywhere) so you catch degradation before it becomes a reputation event.

70-85: Good

Healthy programme but with one or more signals at the warning edge. Identify which input is the lowest contributor to the score and fix that specific item. Do not try to fix everything at once; reputation responds to focused improvement on the weakest signal more than to broad-spectrum tightening.

50-70: Fair

Multiple signals are unhealthy. The calculator's "biggest risk factor" output points to the one with the highest single impact. Address that first, then re-run the score. At this level, scaling volume up usually accelerates damage; pause volume growth until the score is back above 70.

30-50: Poor

Sustained problem; reputation is actively degrading. Common cause: complaint rate above 0.20% for 30+ days, blocklist listing, or major authentication failure. Stop sending to anything but the most engaged segments. Run list hygiene aggressively. Get authentication clean. Expect 60-90 days of focused work before recovery is visible.

Under 30: Critical

Reputation collapse imminent or in progress. Pause all sending except critical transactional. Audit blocklist presence (Spamhaus ZEN, SpamCop, Barracuda). Check authentication is not catastrophically broken. Consider IP rotation only as a last resort — new IPs do not solve a domain reputation problem and can compound it. Recovery from this state often takes 90-180 days and may require third-party deliverability help.