Your Sender Score says 92 and Gmail still files your campaigns under spam: which one do you trust? Gmail. Sender reputation (also called email reputation) is the credit each mailbox provider grants to your sending IP address and domain. Each provider computes it from its own data. Validity’s Sender Score boils it down to a single number from 0 to 100. For Gmail, the reference measure is the spam rate in Google Postmaster Tools: Google asks you to keep it under 0.30% and recommends aiming for 0.10%. This guide covers what to record, with which tool, how often, and how to rebuild a damaged reputation.
Sender Score, Postmaster Tools or SNDS: which indicator for which mailbox
Gmail is read in Google Postmaster Tools, Outlook.com in SNDS, Yahoo in its Complaint Feedback Loop; the Sender Score is an outside benchmark. The statistics from your email platform (opens, clicks, bounces) describe what you sent. The receiving provider’s verdict is read elsewhere: those numbers can stay green while your messages land in the junk folder.
The Sender Score is published by Validity, which bought Return Path, the former publisher named in many guides. You look up an IP address or a domain; the site also asks for a business email address in a form. The 80 and 90 thresholds come from industry habit, not from an official grid: above 90 a reputation is considered very good, below 80 it deserves an investigation, and well below 80 you need to act right away.
Google Postmaster Tools (postmaster.google.com) publishes the spam rate Gmail measures on your domain, with 0.10% and 0.30% as reference points. Microsoft offers SNDS (Smart Network Data Services, substrate.office.com/ip-domain-management-snds/snds), which exposes per-IP data on the Outlook.com side. Yahoo relies on its Complaint Feedback Loop, covered in our article on the feedback loop. Postmaster Tools, SNDS and the Complaint Feedback Loop only see the traffic of their own mailbox service: check all three, with the Sender Score as a complement.
IP reputation or domain reputation: which one to monitor
Monitor both. The domain follows you from one platform to the next, while the IP changes with the platform. IP reputation is tied to the address of the sending server. On a shared IP, it is pooled with other senders. On a dedicated IP, it depends on you alone.
Domain reputation is tied to the domain of the sending address and to the domains that sign your messages with DKIM. Switching sending platform changes the IP. The domain stays the same and keeps its history.
Alignment ties the two together: Google requires the domain in the From field to match the domain validated by SPF or signed by DKIM. Our explanations of DNS records and deliverability walk through the setup. Transactional emails (order confirmations, password resets) can leave from the same IP as your campaigns: a degradation then hits both streams. The article on transactional email deliverability explains how to protect them separately.
The numeric thresholds at Gmail, Yahoo and Outlook
A complaint rate of 0.10% equals 1 message reported as spam per 1,000 messages delivered to the inbox. At 0.30%, that is 3 per 1,000. These figures come from Google (0.10% as the target, 0.30% as the limit) and from Yahoo (0.3%). Microsoft publishes none for Outlook.com.
- Gmail, since February 1, 2024: SPF, DKIM, a DKIM key of at least 1024 bits (2048 recommended), a valid PTR and TLS for all senders to Gmail. Beyond 5,000 messages per day, DMARC (a p=none policy is enough), From alignment on SPF or DKIM and one-click unsubscribe through the List-Unsubscribe-Post header are added. The spam rate in Postmaster Tools must stay under 0.30%, with 0.10% as the target (Google’s sender guidelines).
- Yahoo (senders.yahooinc.com) requires bulk senders to have SPF and DKIM, DMARC at p=none at minimum, one-click unsubscribe honored within 2 days and a spam rate under 0.3%. The Complaint Feedback Loop must be active. The rate is calculated on messages delivered to the inbox (Yahoo best practices).
- Outlook.com has applied requirements since May 5, 2025 to senders of more than 5,000 emails per day: aligned SPF, DKIM and DMARC. Microsoft does not state unambiguously what happens to non-compliant messages (Junk folder, then rejection), so treat these rules as mandatory (Microsoft Tech Community announcement).
The monitoring tools to open in 2026
The table, compiled in October 2026, sorts the tools by what they actually measure. Postmaster Tools, SNDS and the Complaint Feedback Loop reflect one specific provider. The others give an outside opinion.
| Tool | Publisher | What it measures | Input | Use |
|---|---|---|---|---|
| Sender Score | Validity | Score from 0 to 100 | IP or domain | Industry benchmark (80, 90) |
| Google Postmaster Tools | Spam rate on the Gmail side | Domain | Gmail reference, 0.10% and 0.30% thresholds | |
| SNDS | Microsoft | Sending data on the Outlook.com side | IP | Outlook monitoring |
| Complaint Feedback Loop | Yahoo | Complaints from Yahoo recipients | Domain, after sign-up | Complaint detection |
| Talos Intelligence | Cisco | Good, neutral or poor reputation | IP or domain | Detailed third-party opinion |
| MXToolbox | MXToolbox | Presence on blocklists | IP or domain | Blacklist test |
| Barracuda Central | Barracuda | Reputation against the Barracuda list | IP or domain | Spot check |
Postmaster Tools and its 2 threshold levels (0.10% and 0.30%) are documented in the Google help center, SNDS on the Microsoft portal. For blocklists, run the MXToolbox check or the Talos reputation center, then the Barracuda lookup. If an IP is listed, follow the removal procedure described in our guide to avoiding the blacklist.
The monitoring routine, from the weekly reading to the monthly review
A dated history answers one question: since when has the reputation been slipping. Log each reading in a spreadsheet (Google Sheets or Excel) with the date and the value read.
- Every week, open Postmaster Tools, Spam rate section, and note the domain’s rate. Above 0.10% (1 complaint per 1,000 messages), pause sending to the least engaged segments.
- After each campaign, note the hard bounce rate and the number of repeated soft bounces. The definition and causes are in the article on the bounce rate.
- On the same schedule, check SNDS for your IPs and Yahoo’s Complaint Feedback Loop.
- Every month, note the Sender Score of the IP and the domain on senderscore.org (thresholds 90 and 80), then test the blocklists with MXToolbox and Talos.
- After any DNS change or any change of sending provider, check SPF, DKIM, DMARC and the PTR before the next send, for example with the command dig TXT _dmarc.yourdomain.com for DMARC and dig -x followed by the IP for the PTR.
To open Postmaster Tools, add your sending domain at postmaster.google.com and validate it with a TXT record in the DNS; the tool only shows charts once the volume of messages to Gmail is high enough. SNDS requires you to own the IP: on an email platform’s shared IP, ask your provider for these readings. Below 5,000 messages per day, Google’s bulk sender rules are not strictly binding. The same routine remains useful.
Rebuilding a damaged reputation: the 4-step plan
Order matters. Sending more before you have fixed authentication and cleaned the list makes things worse.
Fix authentication
Publish 3 DNS records: SPF, DKIM (your provider’s selector, sometimes as a CNAME) and DMARC on _dmarc.yourdomain.com, starting with v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com: the rua address receives the aggregate reports that show who sends on your behalf. Check that the PTR of the sending IP is valid and that the From is aligned on SPF or DKIM.
Clean the list before the next send
A hard bounce of type 550 5.1.1 (unknown user) proves the address does not exist: remove it at the first rejection. A 5.7.x code points to a block tied to your reputation rather than to the address itself: handle it separately. Spam traps are addresses that belong to no real subscriber and are used to catch purchased or never-verified lists. Validating the list before sending removes invalid addresses before they produce a bounce. Run a sample of your database through CaptainVerify before the next campaign: the share of invalid addresses measured on the sample tells you whether a full cleanup is needed.
Resume sending in stages
Warm-up means raising the volume gradually, stage after stage. Start with the contacts who opened or clicked recently. Move to the next stage only if the spam rate stays under 0.10% and hard bounces are not rising. A new IP or one that has sat idle needs the same method. Plan for several weeks: Gmail, Yahoo and Outlook publish no recovery time.
Stabilize volume, frequency and engagement
Set a regular sending frequency and let the volume grow in stages. Segment by engagement and send inactive contacts a re-engagement email before removing them. Turn on double opt-in for new sign-ups. Put the one-click unsubscribe link in the List-Unsubscribe-Post header: a recipient who unsubscribes does not click “spam”. A subject line that looks like spam also drives up complaints: the guide to forbidden words in emailing lists the wording to avoid.
Frequently asked questions
What Sender Score should I aim for?
At least 90 out of 100 if possible. The score moves mostly with your complaints and bounces: below 80, start with those two readings.
Why does Gmail put my emails in spam despite a good Sender Score?
Validity’s score carries no weight at Gmail. If the spam rate goes above 0.10% or SPF or DKIM alignment fails, the outcome is the same whatever the score.
How long does it take for a reputation to recover?
There is no official timeframe: recovery follows your recent sends, with low spam rates and controlled bounces week after week.
