Find every subdomain
of a domain.

Every hostname under a domain that ever appeared in a public TLS certificate — with certificate counts, first/last seen and live DNS status.

9 hosts · 250 ms

HostCertsFirst seenLast seenDNS
mxtoolbox.com 4 2025-09-22 2026-09-15 ok
*.mxtoolbox.com 4 2025-09-22 2026-09-15 —
knowledgebase.mxtoolbox.com 10 2026-04-23 2026-08-19 ok
blog.mxtoolbox.com 2 2026-06-08 2026-08-09 ok
local.mxtoolbox.com 1 2025-10-15 2025-10-15 ok
www.local.mxtoolbox.com 1 2025-10-15 2025-10-15 nxdomain
studio.mxtoolbox.com 2 2026-07-08 2026-07-08 nxdomain
meetings.mxtoolbox.com 8 2026-04-24 2026-08-20 ok
postfix.mxtoolbox.com 3 2026-06-15 2026-08-14 ok

Programmatic access, with DNS A records: API GET /v1/hosts/mxtoolbox.com (API key for paging).

Shown here: hostnames with a certificate that is valid now or expired within the last 90 days. The full history since 2013 — hostnames whose last certificate expired earlier — is a Pro plan method: GET /v1/hosts-history/mxtoolbox.com.