Domain mail check
MX, SPF, DKIM and DMARC at a glance, and exactly what to fix if something’s off.
What we check
- MX
- Whether the domain’s mail servers exist and respond.
- SPF
- Syntax, the number of records, and a DNS lookup count against the limit of 10.
- DKIM
- By known selectors: whether the key is alive and long enough.
- DMARC
- Whether a record exists, its policy, and whether the reporting address is valid.
Frequently asked
Why does the number 10 matter for SPF?
The SPF spec allows no more than 10 DNS lookups per message check. Exceed it, and the check fails silently, with no warning to the owner.
What happens if I add DMARC with p=none?
Nothing gets blocked; you just start getting reports on who’s sending mail on behalf of your domain.
What’s a DKIM selector?
A name that points to which DNS record holds the public signing key; a domain can have several keys at once, for instance for different mailing services.