Mailbox providers never publish the reputation number they keep for you. What they do publish, in effect, is a checklist: authenticate your mail, stay off blocklists, run a tidy DNS setup and use modern transport security. This checker reads every one of those public signals for a domain and turns them into a single 0 to 100 score.
The result is not a copy of Gmail’s internal rating. Think of it as the technical floor of your reputation. If this score is low, no amount of great content will fully save you. If it is high, the remaining work is list quality and engagement.
How the score is calculated
The score blends four weighted categories. Each category is scored on its own from the checks listed, then combined.
| Category | Weight | What it checks |
|---|---|---|
| Authentication | 30% | SPF record present and valid, DKIM key found across 25 common selectors, DMARC record and policy strength |
| Blocklists | 30% | The IPs behind your MX hosts and your apex A record, checked against 15 public DNSBLs |
| DNS health | 20% | MX records present and redundant, PTR and forward-confirmed reverse DNS on MX IPs, at least two nameservers |
| Infrastructure | 20% | DNSSEC, MTA-STS, TLS-RPT, BIMI and whether MX records point to distinct hosts |
Authentication and blocklists carry the most weight because they are the two areas that cause outright rejections. A missing DMARC record now triggers errors like 550 5.7.26 at Gmail for bulk senders, and a listing on a widely used DNSBL can block mail at the SMTP connection.
The checker also reads your SPF record and lists the sending services it authorises (Google Workspace, Microsoft 365, common ESPs), which is a quick way to spot a platform you stopped using years ago but never removed.
Understanding your grade
| Grade | Score | Meaning |
|---|---|---|
| A | 90 to 100 | Excellent. Authentication, DNS and infrastructure all follow current best practice. |
| B | 75 to 89 | Good. Delivery should be reliable, with one or two improvements available. |
| C | 60 to 74 | Fair. A gap such as a weak DMARC policy or no PTR is likely costing you some inbox placement. |
| D | 40 to 59 | Poor. Missing authentication or a blocklist hit is probably causing filtering or bounces. |
| F | 0 to 39 | Critical. Major providers are likely rejecting or junking a large share of your mail. |
Most domains that send regularly through a reputable provider land in the B range on the first run. The usual things holding them back are a DMARC policy stuck at p=none, no MTA-STS policy and a single MX host.
Reading the fix list
Below the grade you get a prioritised list of fixes, sorted by how many points each one is worth and how much it affects real delivery. Work from the top down.
A typical list for a mid-sized sender looks like this:
- DMARC policy is
p=none. Move top=quarantineonce reports show all your sources pass. - SPF uses 9 of 10 DNS lookups. Remove unused includes before adding another service.
- MX IP has no PTR record. Ask your mail host to set reverse DNS.
- No MTA-STS policy published. Add one to enforce TLS for inbound mail.
Each item links to the tool that checks it in depth: the SPF checker, DMARC checker, blacklist checker and reverse DNS checker. Fix one item, rerun the score and confirm it moved.
What public DNS cannot tell you
Be clear about the limits. Gmail, Outlook and Yahoo base much of their filtering on how recipients react: opens, replies, deletes without reading and spam complaints. None of that is visible to an outside tool.
For that half of the picture, use the providers’ own dashboards:
- Google Postmaster Tools shows your domain reputation at Gmail, your user-reported spam rate and authentication pass rates. Keep the spam rate under 0.1% and never let it reach 0.3%.
- Microsoft SNDS shows data for IPs you control, including complaint rates and trap hits at Outlook.com.
- Your ESP’s reports show bounces per campaign. Keep hard bounces under 2%.
A high score here plus healthy numbers in Postmaster Tools is the combination you want. A high score with a poor Postmaster rating points you straight at list quality and content, which our guide to improving email deliverability covers step by step.
Common reasons for a low score
No DKIM found. Either DKIM is not set up, or your provider uses a selector outside the common set. Check a real message header for the s= tag and test that selector directly.
Blocklist hit on the apex A record. Your website IP is listed, often because shared hosting puts you next to a spammer. This matters less than an MX IP listing but can still affect URL reputation. Moving the site or asking the host for a clean IP usually fixes it.
Single MX host. One MX record means one point of failure for inbound mail, including bounce and reply handling. Most hosted providers give you several.
Multiple SPF records. Two TXT records starting with v=spf1 make SPF return a permanent error, which zeroes most of the authentication score. Merge them into one.
DMARC with no reporting. A DMARC record without rua gives you policy but no visibility, so you cannot safely tighten it.
How to raise your score quickly
The fastest gains come from authentication, because it is fully under your control and changes take effect within hours.
- Publish one SPF record covering every service that sends as your domain. Use the SPF generator if you are starting from scratch.
- Turn on DKIM signing in each sending platform with a 2048-bit key.
- Publish DMARC with
p=noneand aruaaddress, then step up toquarantineandreject. The DMARC generator builds the record. - Check blocklists and follow each list’s delisting process. Our blacklist removal guide walks through it.
- Add MTA-STS and TLS-RPT, and enable DNSSEC if your DNS host supports it.
If you send through a platform that manages authentication for you and offers a dedicated IP (SendPulse’s SMTP Pro plan includes one, as do the higher tiers of SendGrid and Mailgun), most of steps 1 to 3 come down to copying records from the domain settings page, and your IP reputation depends only on your own sending. For the full background on how providers score senders, read what is sender reputation.