Methodology

InboxMonitor reads public DNS once a day, and again when you run a check. It does not send mail, and it does not measure inbox placement, bounces, or replies.

Checks

• SPF: the TXT record, syntax, the all mechanism, and DNS lookup count. More than 10 lookups fails. 8 to 10 is a watch.
• DKIM: common selectors, plus any selector you save. The row names the key type and length. Under 1024 bits is a warning. 1024 bits is a note recommending 2048. An empty p= means that selector was revoked.
• DMARC: the record, policy, and rua addresses. A missing record is critical. p=none is a warning.
• MX: whether the domain publishes mail exchange records.
• PTR and forward-confirmed reverse DNS for the domain's own sending IPs. Shared Google and Microsoft include IPs are skipped.
• Domain age and expiration from RDAP when the registry publishes those dates.
• Blocklists: PSBL and 0spam, queried against IPs in the domain's A record, MX hosts, and explicit SPF entries. Refusals, timeouts, and SERVFAIL are not treated as clean.

Score

The score starts at 100 and is clamped between 0 and 100. Points come off for problems:

• SPF missing 30, invalid syntax 28, over 10 lookups 25, +all 22, ?all or no all 8, 8–10 lookups 6, a temporary DNS error 6.
• DKIM: a saved selector with no key 24, a revoked selector and no other live key 8, RSA under 1024 bits 16. A 1024-bit key is noted and does not subtract. No key at the common selectors, when you have not saved one, is information only.
• DMARC missing 24, invalid 16, p=none 10, no rua 2, a temporary DNS error 4.
• MX missing 8, a temporary DNS error 4.
• Blocklist: the first listing is 30, each extra listing is 5, capped at 40. Policy lists and checks that did not answer do not subtract.
• PTR missing 8, unconfirmed 6.
• Domain age under 7 days 12, 7 to 29 days 6.

What the labels mean

The overall label is Healthy, Watch, or At risk. A row is Pass, Watch, or Fail.

• At risk: any critical finding, or a score under 60.
• Watch: any warning, or a score under 85.
• Healthy: neither of those.

The first check is a baseline. Later checks email you when a result gets worse, and again when that problem clears. Plans and prices.