What the MX lookup shows
- Every MX record for the domain, sorted by priority.
- IP addresses each mail server resolves to. A server name that does not resolve is a configuration error and mail to it fails.
- The email provider, detected from the server names: Google Workspace, Microsoft 365, Zoho, Proofpoint, Mimecast and others.
- Null MX and missing MX, which mean the domain cannot receive email.
Why MX records matter for email lists
An MX check is the first real test an email verifier runs after syntax. If a domain has no working mail server, every address at it bounces, no matter how valid it looks. Typos such as gmial.com or expired company domains are common in sign-up forms and purchased lists, and each one becomes a hard bounce that damages your sender reputation.
Knowing the provider also helps. Large providers such as Google and Microsoft apply their own anti-abuse rules and sometimes give deliberately ambiguous answers to mailbox checks, while corporate gateways like Proofpoint or Mimecast may accept all mail at the edge. That is why good verification combines MX lookups with SMTP checks and catch-all detection.
How to fix MX problems on your own domain
Mail server does not resolve
The MX record must point to a hostname with an A or AAAA record, never directly to an IP address or to a CNAME. Correct the hostname to the one your email provider gives you.
Old provider still listed
After switching providers, remove the old MX records. Senders may otherwise deliver to the old servers, and that mail is lost or delayed.
Only one MX record
Hosted providers run redundant infrastructure behind one or several names, so a single record is often fine. If you run your own server, add a backup MX with a higher priority number.
From domains to mailboxes
An MX lookup answers "can this domain receive mail?". To answer "does this address exist?" for a whole list, use email verification: it adds SMTP mailbox checks and flags catch-all, role-based and disposable addresses so you only send to contacts that will receive your mail.