DNS Record Lookup

What each record type does

Understanding TTL

Every record carries a time to live, measured in seconds. It tells resolvers how long they may keep serving a cached copy before asking again. A TTL of 300 means five minutes; 86400 means a full day.

This is why DNS changes are not instant. If you update a record that had a 24 hour TTL, some resolvers around the world will keep handing out the old value for another 24 hours. The standard trick before a planned migration is to lower the TTL to a few minutes a day in advance, make the change, then raise it again once traffic has settled.

Why answers differ between tools

DNS is a distributed cache, not a single database. This page queries a public encrypted resolver. Your laptop probably uses whatever resolver your router advertised, which may be your ISP's. Each one holds its own cached copies with their own expiry, and some networks deliberately rewrite answers for filtering or captive portals. Seeing two different results is normal during a change, and is itself useful information.

Reading a mail setup

To check whether a domain can receive mail, look at its MX records: the lowest preference number is tried first. To check whether it can legitimately send mail, read the TXT records for an entry beginning v=spf1, which lists the servers allowed to send on its behalf. A domain with no SPF record will see much of its mail land in spam.