What this configuration means
Each section below is shown because the observed records match its condition. The explanations are reviewed text selected by the data, not generated from it.
DMARC requests quarantine
github.com asks receivers to quarantine mail that fails alignment. Unaligned mail is routed to spam rather than refused, which limits the damage from spoofing while leaving a margin for misconfigured legitimate senders. The usual next step is p=reject after confirming through aggregate reports that no legitimate source still fails.
Subdomains carry a different policy
The record sets sp=reject while the organizational policy is p=quarantine. Subdomains of github.com are therefore treated differently from the apex — a stricter policy that requires every sending subdomain to have its own aligned path.
SPF ends in soft fail
Unlisted sources produce softfail: receivers are asked to accept but mark the message. Under DMARC a softfail counts as an SPF failure, so the practical protection comes from DMARC policy rather than from ~all itself. Moving to -all is appropriate once the sender inventory is confirmed complete.
SPF is close to the lookup limit
Recursive resolution of the record uses 9 of the 10 DNS-querying mechanisms RFC 7208 allows. The next platform added — or a vendor expanding its own include — is likely to push evaluation into PermError, at which point SPF stops working for every sender at once.
A single mail exchanger
Inbound mail depends on one published host, github-com.mail.protection.outlook.com. That host belongs to Microsoft 365, which provides its own redundancy behind the name. A single MX is normal for hosted mailbox providers and a risk for self-hosted ones.
DKIM selectors are published
7 selectors resolve under _domainkey.github.com: google, selector1, selector2, s1, s2, k1, smtpapi. Selector names often identify the sending platform, and each represents a signing key that can produce an aligned DKIM path for DMARC — the path that survives forwarding.
No transport-security policy
github.com does not publish MTA-STS, so senders negotiate TLS opportunistically and fall back to clear text if an attacker strips the upgrade. Publishing TLS-RPT first, then MTA-STS in testing mode, adds transport protection for inbound mail without risk to delivery.
Sending platforms visible in DNS
Public records reference 5 platforms: Google Workspace, Mailchimp, Microsoft 365, SendGrid, Zendesk. Each SPF include or DKIM selector is an authorization that someone must own. Platforms no longer in use remain authorized until the records are removed.
Change history
No change has been observed since the first snapshot on 2026-09-08. The domain is re-checked regularly and a new entry appears here when any record above changes.
How to read this report
The grade summarizes two records only: A means an enforcing DMARC policy with SPF hard fail; B enforcing DMARC with SPF; C monitoring-only DMARC or a weak SPF qualifier; D one of SPF or DMARC missing; F neither published. It is a prioritization aid for the public control plane, not a statement about deliverability, reputation or the security of the organization behind the domain.
DMARC policy is discovered with the RFC 9989 DNS tree walk, so a subdomain with no record of its own is reported with the organizational policy it inherits. DKIM selectors are discovered from common names only; a domain may sign with selectors this check does not try. Everything on this page comes from public DNS as observed on 2026-09-09; caches and split-horizon DNS can show different values elsewhere.
If you operate github.com and want a record corrected or the report removed, contact Mailybox.