What a sender reputation is made of
A receiving provider cannot read intent, so it reads behavior. For each sending domain and each sending IP it keeps a record of what happened to the mail: how often recipients reported it as spam, how much of it went to addresses that do not exist, how often it was opened, replied to, moved or deleted unread, whether the volume climbed or jumped, and whether the mail authenticated. The judgement it draws from that record is the sender reputation, and it is what decides, for mail the server has already accepted, whether the message is filed to the inbox or to spam.
- Domain reputation follows the domain in the From address and the domain that signs with DKIM. It is the one a sender on Google Workspace or Microsoft 365 owns.
- IP reputation follows the address the mail left from. On a hosted provider the IPs are shared and the provider manages them; on your own server or a relay they are yours.
- It is per provider. Gmail, Outlook.com and Yahoo each keep their own, on their own users' behavior, which is why placement differs by provider for the same message.
Who keeps a score, and on what scale
- Google, in Postmaster Tools: a domain reputation and an IP reputation on four tiers, Bad, Low, Medium and High, defined in Google's own words on the Postmaster domain reputation page, plus the user-reported spam rate. Shown only to the domain's verified owner.
- Microsoft, in SNDS: filter results and complaint data per registered IP for Outlook.com, plus the Junk Mail Reporting Program for the complaints themselves. Microsoft 365 tenants filter through Exchange Online Protection with their own policies. No domain tier is published.
- Yahoo publishes no console for reputation; its sender pages describe the practices it scores on and the deferrals it applies to high-complaint domains.
- Third parties: Validity's Sender Score is a per-IP score behind a free account; Cisco Talos publishes a reputation lookup used by Cisco gateways. Both are estimates from that vendor's own traffic, not the providers' verdicts.
Is it public?
The providers' own scores are not. What is public is the evidence they are built from: whether the domain or its IPs sit on a blacklist, whether SPF, DKIM and DMARC exist and pass, whether the sending address has forward-confirmed reverse DNS, and how old the domain is. The domain reputation checker reads all of that in one report and gives the fix order; the providers' consoles are linked from it for the half only they can show.
How to check yours
- Gmail: verify the domain in Postmaster Tools and read the domain reputation and spam rate dashboards. Google shows data only on days with enough volume, so a small sender may see nothing while still being scored.
- Outlook.com: register the sending IPs in SNDS and enrol in the Junk Mail Reporting Program.
- The result: a placement test, which shows where a message actually lands per provider. The consoles show standing; the test shows the verdict on a message.
What a good score looks like
At Google, a High tier with the spam rate under the 0.10% line Google's sender guidelines ask for. At Microsoft, a green SNDS status with no trap hits. On a third-party tool, a good number on that tool's scale. None of them is the goal: a domain can be High at Gmail and in Junk at Outlook.com, and a good score at every console still says nothing about the Promotions tab. Placement is the goal, and the score is how the provider explains its placement decisions to you.
What MailStrike's Inbox Reputation Score reads
MailStrike's dashboard shows an Inbox Reputation Score per mailbox and account-wide. It is not a provider's verdict and it is not a third-party estimate: it is read from where the warming mail actually lands across the MailStrike network, checked on the receiving side for every message sent, over a rolling window. It rises as the domain's standing rises at the providers the network spans. Clearing a mailbox to send needs more than the score: it has to have warmed for 21 days or more and the domain has to be at least 30 days old, because a young domain with a few days of history reads well and does not yet survive real outbound.
When a score drops
In rough order of likelihood, from what the network sees:
- Real outreach started at a volume above what the domain had earned, to a list with low engagement.
- A DNS change broke SPF, DKIM or DMARC, or a new sending service was added without aligning it.
- A provider temporarily blocked or rate-limited a mailbox.
- Warming was paused, so the engagement record stopped growing while campaigns kept drawing on it.
- A complaint or bounce spike from a campaign rather than from warming.
How a poor reputation is repaired
Records are fixed in an afternoon; the record of behavior takes weeks. Stop sending to the addresses producing the complaints and bounces, fix authentication and alignment, clean the list, and then rebuild the engagement record: warming on a ramp while campaigns stay small and to engaged recipients, with a placement test before each step up. The recovery guide walks through it.