An MX record is a DNS record that tells the internet where to send email for your domain. When someone sends an email to you@yourdomain.com, the sending server performs a DNS MX lookup on yourdomain.com and connects to the mail server returned. Without a valid MX record, no email can be received.
MX records are separate from sending authentication records (SPF, DKIM, DMARC). A domain can have MX records for receiving email and SPF/DKIM for sending email — these are independent configurations. Many domains used only for outbound sending (transactional email subdomains) have no MX records intentionally.
MX record structure and priority
Each MX record has two fields: a priority number and a hostname. Lower priority numbers are preferred — if you have two MX records with priorities 10 and 20, the sending server tries the priority-10 server first and only falls back to the priority-20 server if the primary is unavailable.
A typical Google Workspace MX configuration has five records: ASPMX.L.GOOGLE.COM at priority 1, and four ALT*.ASPMX servers at priorities 5 and 10. Microsoft 365 uses a single MX record at your-domain.mail.protection.outlook.com. CNAME records cannot be used at the MX target — the MX hostname must resolve to an A record, not a CNAME.
Checking your MX record
From the command line: dig MX yourdomain.com or nslookup -type=MX yourdomain.com returns all MX records in priority order. Then dig A on each target hostname to confirm it resolves to an A record (not a CNAME — that violates RFC 2181 and some strict receivers reject mail outright). A web checker that walks the same chain and flags CNAME-at-MX errors is linked from the related box.
Common MX record problems: missing MX record (domain receives no email), CNAME at MX target (RFC violation, many servers refuse), multiple MX records pointing to the same server (valid but unnecessary), and MX records pointing to a non-existent hostname (messages deferred or bounced).
Frequently asked questions
01Do I need an MX record to send email?
No. MX records control where email is received, not sent. To send email, you need a server or ESP and proper authentication (SPF, DKIM). Some mail servers check for a valid MX record on the sender's domain as a spam signal — a domain with no MX records might be treated as suspicious — but it is not required to actually transmit messages.
02What happens if my MX record is wrong?
Senders to your domain will receive a bounce with a code indicating the destination server could not be reached (no MX record: DNS lookup failure) or that the connection was refused (wrong server). Email to your domain will be lost or deferred until the DNS is corrected and propagates (typically 0–48 hours depending on TTL).
03Can I have two email providers with one domain?
Not simultaneously for the same addresses. An MX record points a domain to a single mail platform. If you have MX records for both Google Workspace and Microsoft 365, only the lower-priority (preferred) one will receive email. To split addresses between providers, use subdomains: staff@mail.yourdomain.com can have different MX records than info@yourdomain.com.
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