Check any domain's mail servers (MX records), detect the email provider, and grade MX health. Instant and free — no signup.
An MX (Mail Exchange) record is the DNS record that tells the world which mail server accepts email for a domain. A domain can list several MX hosts with different priority values (lower = tried first) for redundancy. If a domain has no MX record and no fallback A record, it simply cannot receive email — a guaranteed hard bounce.
An MX check tells you a domain can receive mail, but not whether a specific mailbox exists. To confirm a real address, use the email validator (SMTP probe) or clean a whole list with the bulk email cleaner. For the technical deep dive, see DNS & MX records explained.
An MX (Mail Exchange) record is a DNS record that tells other mail servers which host accepts email for a domain. A domain can have several MX records with different priority values; lower numbers are tried first. Without a valid MX (or a fallback A record), a domain cannot receive email.
Enter the domain (e.g. example.com) above and click Look up MX. This tool queries DNS live and shows each MX host with its priority, detects the email provider, and grades the MX setup. You do not need an account.
The grade reflects MX setup quality: A means multiple MX hosts on a recognized provider (redundant and reliable), B means either multiple hosts or a known provider, and C means a single unknown host. It is a quick signal of deliverability robustness, not a guarantee.
What is an MX record? A Mail Exchange (record MX) is a DNS resource record specified in RFC 1035 and RFC 5321 that directs internet mail transfer agents to the specific hostnames responsible for accepting incoming email for a domain. Every MX record consists of two fields: a 16-bit unsigned integer preference (MX record priority, from 0 to 65535) and a fully qualified domain name (FQDN) that must resolve to an A or AAAA IP address (never a CNAME).
How does MX record priority work? Sending servers always attempt delivery to the MX hostname with the LOWEST preference number first (for example, priority 1 or 10). If two MX records share the exact same priority number, sending servers load-balance connections equally across both hosts. If the primary MX server is unreachable or returns a 4xx temporary deferral, the sending MTA automatically fails over to the next higher priority number (e.g., priority 20 or 30). Modern Google Workspace domains use a single consolidated MX record (1 smtp.google.com), whereas legacy Google Workspace setups use five records (1 aspmx.l.google.com, 5 alt1/alt2, 10 alt3/alt4).
| Mail Infrastructure Provider | Canonical Record MX Hostname & Priority | Inbound Gateway Behavior & TLS Support |
|---|---|---|
| Google Workspace (2026 Consolidated MX) | Priority 1 → smtp.google.com (or 1 aspmx.l.google.com) | Anycast global load-balancing with mandatory TLS 1.3 & FCrDNS check |
| Microsoft 365 Exchange Online | Priority 0 → <tenant-guid>.mail.protection.outlook.com | Single priority-0 EOP endpoint with SmartScreen & SNDS reputation filtering |
| Yahoo Mail / Ymail / AOL Unified MTA | Priority 1 → mta5.am0.yahoodns.net, mta6.am0.yahoodns.net, mta7... | Equal-priority round-robin cluster with 421 TSS04 rate-limit throttling |
| Null MX Record (RFC 7505 Non-Sending Domain) | Priority 0 → . (Single period target) | Explicitly tells all MTAs that the domain never accepts incoming email |