Blue Folder

DNS & MAIL SERVERS

DNS & mail server tools

Look up MX records and detect who runs a domain's email, read every DNS record at once, watch a change propagate across the internet, and check whether a mail server is on an email blocklist. Everything runs in your browser over encrypted DNS-over-HTTPS — nothing is logged.

MX & host detector All-in-one DNS Propagation Blocklist (DNSBL)

MX lookup & email host detector

Enter a domain to see its mail exchangers, sorted by priority — then find out which provider actually handles its email.

All-in-one DNS lookup

One search returns A, AAAA, MX, TXT, NS, CNAME and CAA records together — a full snapshot of a domain's DNS.

Email that belongs to you. Point your own domain's MX records at Blue Folder Mail and get an encrypted inbox for every address you own — on Mac and iPhone. See plans →

DNS propagation checker

Changed a record? Query several independent public resolvers at once and see whether they agree yet. Matching answers mean the change has propagated.

Email blocklist (DNSBL) checker

Enter a mail server's domain or its IPv4 address to check it against well-known email blocklists. If a domain is given, its A record is resolved first.

Blocklists often rate-limit or block lookups made through public DNS resolvers. A “couldn't check” result means exactly that — it is not the same as being listed. Only a genuine listing is flagged, and anything uncertain is shown neutrally.