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.

15 hosts · 341 ms

HostCertsFirst seenLast seenDNS
mailsec.ca 14 2026-04-25 2026-09-22 ok
*.mailsec.ca 3 2026-07-21 2026-09-18 —
attacker-console.mailsec.ca 4 2026-05-09 2026-07-08 nxdomain
bimi.mailsec.ca 5 2026-05-02 2026-08-31 ok
app.mailsec.ca 9 2026-04-19 2026-09-22 ok
backoffice.app.mailsec.ca 7 2026-06-04 2026-09-22 ok
reporting.app.mailsec.ca 9 2026-04-19 2026-09-22 ok
management.app.mailsec.ca 10 2026-04-19 2026-09-22 ok
toolbox.app.mailsec.ca 10 2026-04-19 2026-09-22 ok
mta-sts.mailsec.ca 5 2026-04-22 2026-08-20 ok
app.dev.mailsec.ca 3 2026-04-19 2026-06-18 nxdomain
reporting.app.dev.mailsec.ca 3 2026-04-19 2026-06-18 nxdomain
management.app.dev.mailsec.ca 3 2026-04-19 2026-06-18 nxdomain
toolbox.app.dev.mailsec.ca 3 2026-04-19 2026-06-18 nxdomain
www.mailsec.ca 8 2026-05-16 2026-09-22 ok

Programmatic access, with DNS A records: API GET /v1/hosts/mailsec.ca (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/mailsec.ca.