Reputation Basics: Domain vs IP
Every major mailbox provider maintains two related but distinct scores. Domain reputation follows the visible From: domain (the string a recipient reads in the inbox). IP reputation follows the specific IP address the message was sent from. The two are usually correlated but rarely identical — a shared ESP pool IP can be dragged down by a bad neighbour, while the same sender’s domain reputation stays High.
Gmail weights domain reputation more heavily than IP reputation for inbox placement decisions. Microsoft scores per-IP through SNDS and ties per-IP colour back to the domain separately. Yahoo weighs engagement on the From: address most heavily, and reports counters in its Feedback Loop. The composite that emerges on the Sender Reputation Guide dashboard is the sum of those provider-specific views — and the per-provider breakdown on the same dashboard is what tells you which one is dragging the composite down.
The shared infrastructure underneath all four providers is the same handful of signals: SPF / DKIM / DMARC alignment at the receiving hop, PTR presence, complaint rate per-IP and per-domain, trap-hit counts, and the historical pattern of the domain. A sender that scores High on all four providers has the same profile against every measurement — clean authentication, low complaint rate, no blocklist hits, consistent engagement. None of the four is a magic input; the composite is read as a pattern.
Gmail Postmaster Tools: Domain and IP Reputation
Gmail surfaces sender reputation inside Postmaster Tools (postmaster.google.com). The dashboard reports four per-domain signals: domain reputation (a band — High / Medium / Low), IP reputation (same band), spam complaint rate (a percentage — 0.1% is safe, 0.3% triggers throttling), and the domain-vs-IP traffic split (a diagnostic that shows where reputation is concentrated). Postmaster Tools does not publish per-message inbox placement or numeric scores — the reputation band is the cleanest single signal Gmail makes public.
The domain reputation band is fed by SPF / DKIM / DMARC alignment on every message, recipient engagement (opens, replies, moves-from-spam) over rolling windows, complaint rate per-domain, and blocklist status on the sending IP. A High-domain / Low-IP profile still places well — the inverse does not. The fastest single move on a Medium-to-Low drop is fixing authentication alignment (usually an ESP signing with a vendor subdomain) — the sub-component recovers inside an hour of DNS propagation, the Postmaster band follows in 4–8 weeks.
The Postmaster dashboard is the closest read of Gmail-side reputation you can get without running a seed list. The full enrollment walkthrough is in the Gmail Postmaster Tools setup guide — enroll your visible From: domain, publish the DNS verification record at the apex, wait 5–15 minutes for propagation, and the data begins populating once you have sent enough mail from the domain to register real Gmail volume.
See your sending reputation for free
The free deliverability score checker reads the same five sub-components Gmail and Outlook weigh — authentication, engagement, complaint rate, blocklist status, IP / domain history — and surfaces them on a 0–100 scale with the top 3–5 risk factors ranked. No signup required.
Run the free verdict →Microsoft SNDS and JMRP: Outlook.com Per-IP Reputation
Microsoft scores Outlook.com sender reputation per-IP through SNDS (Smart Network Data Services). Once you enroll at postmaster.live.com/snds, the dashboard publishes a daily colour band for each enrolled IP — green = healthy, yellow = bulk-marked, red = filtered — alongside per-IP complaint rate, trap-hit counts, and the message volume from each IP. The colour band moves daily and is the single cleanest per-IP reputation signal Microsoft publishes.
SNDS is gated purely on per-IP data, not on authentication results. The colour band is fed by complaint rate, trap hits, and the volume pattern per-IP. The fastest single move from yellow back to green is fixing DKIM alignment — Microsoft weighs JMRP feedback heavily when re-classifying an IP, and JMRP enrolment (the per-message complaint feedback loop) is gated behind several weeks of clean SNDS data.
JMRP (Junk Mail Reporting Program) is the per-message complaint loop. Every time an Outlook.com recipient marks one of your messages as junk, you receive a forensic copy in your JMRP inbox — same headers the recipient saw, same content, same IP, same DKIM signature. JMRP enrolment is gated behind an application review and is only approved after SNDS data has stabilised clean. The full enrollment walkthrough is in the Microsoft SNDS reputation guide.
SenderScore and Cisco Talos: The Sender-Score Index and the Reputation Database
SenderScore (senderscore.org) is Return Path / Validity’s reputation index — a per-IP score on a 0–100 scale, recomputed continuously as fresh data accumulates. SenderScore is consulted by mid-size corporate gateways and some enterprise anti-spam vendors; it is not surfaced by Gmail or Microsoft directly, but a poor SenderScore can produce silent spam-folder routing that has no bounce to point at it. The recovery mode is volume + engagement on a clean stream — SenderScore has no instant delist button.
Cisco Talos (talosintelligence.com) is Cisco’s per-IP and per-domain reputation database, scored on a neutral / poor / bad scale. It is consulted by IronPort appliances and Cisco ESA gateways at enterprise receivers — a significant segment of the receiving internet. Talos reputation climbs back over weeks of consistent clean sending, just like SenderScore; there is no instant delist path either.
Both SenderScore and Talos are the silent signals — no public Postmaster-style dashboard, no per-message colour band, but a real effect on inbox placement. The fastest high-level read is the free sender domain or IP blacklist risk checker, which returns a 0–100 risk score across those signals. For per-list detail, use the blacklist lookup, which reads per-list severity with the AI analyst, paired with the multi-DNSBL blocklist checker, which queries SenderScore and Talos alongside Spamhaus, Barracuda, and SORBS in one pass. A Talos "poor" verdict or a SenderScore drift below 70 in the same window as a Postmaster domain drop usually means a sustained sending pattern has crossed a threshold — pause, audit, and re-pace.
How Each Metric Moves Together
The four provider-side dashboards (Postmaster, SNDS, SenderScore, Talos) report signals that overlap — clean authentication moves all of them; a Spamhaus listing pulls all of them down. Some signals lag and some lead. Authentication alignment recovers inside an hour of DNS propagation and Postmaster follows in days; SNDS colour follows in 1–2 weeks; SenderScore and Talos in 4–6 weeks. A single configuration change therefore moves the composite faster than the worst single signal — the pattern of which band recovers slowest is what tells you which provider is currently the bottleneck on a recovery.
The most common failure mode that drags all four providers down together is a vendor-subdomain mismatch — your ESP signs with d=mailvendor.net while the visible From: is your brand. Postmaster domain reputation drops first; SNDS colour shifts to yellow on the affected IP; SenderScore drifts; Talos scores the same IP poor. The shared cause becomes visible in the per-component breakdown — fix authentication, and all four follow on their own recovery curve.
The trustworthy diagnostic is the daily composite on the Sender Reputation Guide dashboard, with the per-component breakdown on the same page. Read the trend before reading any single point reading — a single point can be noisy; the trend over weeks tells you whether the most recent campaign moved the composite the right direction.
How to Lift a Low Reputation Rating
The recovery loop is the same for every provider. Pause non-essential sends, prune non-engaged recipients, fix the upstream signals (DKIM alignment, missing PTR, complaint rate, blocklist status), then re-ramp at a slower curve than the one that produced the drop. A Medium-to-High recovery runs 4–8 weeks of disciplined execution. A High-to-Low drop is slower — 3–4 months — and may require moving to a fresh dedicated IP and a clean subdomain.
The fastest single move is fixing DKIM alignment. Run the SPF / DKIM / DMARC checker on the sending domain; the per-protocol pass / warn / fail verdict tells you whether the d= signing domain aligns with the visible From: domain. Configure the ESP to sign with a subdomain of your brand (e.g. mail.yourbrand.com) for both the envelope sender and the DKIM signing domain; re-publish the SPF record to include the new subdomain. Authentication alignment recovers inside an hour of DNS propagation; the per-provider scores follow on their own recovery curves.
The slowest recovery path is a brand-new dedicated IP that has not been used before. Even with clean authentication and a High-domain reputation carry-over, the IP itself starts with no engagement history and has to climb the same warm-up curve a fresh domain would. The matching warm-up schedule applies — start at ≤20 per day in week 1, climb to a higher volume only after full weeks of clean Postmaster data, hold for an extra week when any signal turns red. The composite on reputation usually tracks behind that curve by 4–6 weeks.
Monitor reputation daily
The Sender Reputation Guide dashboard polls Gmail Postmaster, Microsoft SNDS, the DMARC RUA aggregate reports, and listing status on Spamhaus / Barracuda / Talos / SenderScore / SORBS every day. The 0–100 composite on the dashboard rolls those signals into a single score with the strongest negative drivers ranked first.
Common Mistakes
- Treating Postmaster domain reputation as an IP metric. The domain reputation band follows the visible From: domain, not the IP. A High Postmaster IP score on a Low domain score still places badly at Gmail; the inverse still places well. Read the dashboard by domain first, IP second.
- Switching ESPs without re-pacing warm-up. A new ESP usually brings a new shared-pool IP — even if the visible From: domain stays the same, the IP reputation starts from zero. The matching warm-up schedule applies to the new IP from day one, regardless of the carry-over domain reputation.
- Reading Postmaster domain reputation as a numeric score. Gmail publishes a band — High / Medium / Low — not a number. The composite in the deliverability-score dashboard is the closest numeric approximation, but the band is what Gmail actually surfaces. A High verdict means sustained clean sending over weeks; a single spike in complaint rate does not flip the band on its own.
- Skipping SNDS enrollment on an Outlook-heavy list. Outlook.com recipients are a meaningful slice of most B2B audiences. SNDS data is the cleanest per-IP reputation signal Microsoft publishes. An unenrolled IP leaves you guessing about yellow / red colour shifts on the only place you can read them.
- Treating SenderScore / Talos as decorative. Neither score shows up at Gmail or Microsoft directly, but both are read by enterprise gateways. A SenderScore below 70 or a Talos "poor" verdict is what produces silent spam-folder routing with no bounce to point at it — the gap that lets a sender believe things are fine while inbox placement is dropping on a third of their list.