How Inbox Providers Actually Score Your Domain (and What You Can See)

There is no deliverability score you can look up. Mailbox providers decide on their own signals, keep the weighting private and change it without notice, and the same message can reach the inbox at Gmail while being throttled at Outlook. What can be said is which signals they're known to use and where each one shows up for you.

The signals that matter across providers

• Authentication: SPF, DKIM and DMARC passing and aligned. Without it you're rejected or filtered before reputation is even considered
• Complaints: how often recipients mark your mail as spam. It's the clearest statement a recipient can make, and the one that moves reputation fastest
• Bounces to invalid addresses: a high share tells providers your list is collected carelessly
• Spam traps: hitting addresses that never opted in suggests scraped or neglected lists
• Engagement: replies, messages moved out of spam, messages read or deleted unread. Gmail leans heavily on how its own users treat your mail
• Consistency: sudden spikes in volume from a quiet sender look like a compromised account
• Content and links: the wording, the formatting and above all the reputation of the domains in your links

Domain, IP and the links inside

Reputation attaches to several things at once: the sending IP, the domain in your From address and DKIM signature, and the domains that appear in your links. IPs are easy to change and domains aren't, so Gmail in particular weights domain reputation heavily. That is why changing IP rarely rescues a burned domain, and why a blocklisted tracking domain can hurt a message sent from a clean one.

What each provider shows you

• Google Postmaster Tools: domain-level spam rate, authentication and compliance status, once you send enough volume to Gmail. It shows nothing for a small sender
• Microsoft SNDS and JMRP: IP-level data and a complaint feedback loop, aimed at senders who control their IPs
• Yahoo's complaint feedback loop: reports complaints per DKIM domain, so you can suppress the people who complained

Between them they don't give a single number, and they don't need to. The practical way to read your standing is outside-in: where seed messages land, how deferrals and rejections read, and whether reply rates move.

Reading it from the outside

• Placement tests across providers show whether you're reaching the inbox, a tab or spam
• The wording of rejections and deferrals tells you what the provider objects to, which is why bounce messages are worth decoding rather than skipping
• Blocklist checks catch listings that affect many providers at once
• A sudden drop at one provider while others are steady points at that provider's own signals; a drop everywhere points at a shared cause such as a listing or an authentication failure

Send a message to seed mailboxes and see where it lands

Check a domain or IP across blocklists

What Google Postmaster Tools v2 tells you

You can't read a provider's mind, but you can read what it does to your mail. Placement, rejections and complaints are the score.