What does a bulk MX lookup show?
A bulk MX lookup reads the MX records of many domains in one go and names the service each one receives mail with, such as Google Workspace, Microsoft 365 or a security gateway. Paste up to 15 domains or email addresses; repeats are removed, and an address counts as its domain.
Reading the result
A count by provider comes first, then each domain with its status and its most preferred MX hosts. The provider is the one receiving at the lowest MX number. A domain whose MX mixes two providers is marked. Gateways such as Proofpoint, Mimecast and Barracuda are named as gateways, because the mailbox provider behind them does not show in DNS.
Beat runs on the same engine, on a schedule, across all 41 checks and 25 blacklists. What it adds is asking again, noticing when an answer changes and telling you what to do about it.
Common problems it finds
No MX at all
The domain publishes no MX, so senders fall back to its address record (RFC 5321). On a list of contacts, mail to such a domain often bounces.
A null MX
The domain declares that it accepts no mail (RFC 7505). Addresses at it are undeliverable by the owner’s own statement.
A domain that does not exist
NXDOMAIN: the name is not registered or has lapsed. Every address at it hard bounces, so remove it from a list before sending.