MEmail Deliverability Glossary

MX Record (Mail Exchange Record)

A DNS record specifying which mail servers accept incoming email for a domain. Correctly configured MX records are required for warm-up replies to reach your inbox.

An MX record is a DNS record that specifies which mail servers handle incoming email for a domain. It is used by sending servers to know where to deliver messages.

Relevance to warm-up: When warm-up network accounts reply to your warm-up emails, their responses are delivered to the mail server specified in your domain's MX record. A correctly configured MX record is required for replies to reach your inbox — if replies cannot be delivered, an important engagement signal is lost.

MX record priority: Multiple MX records can be configured with priority values (lower number = higher priority). The sending server always tries the highest-priority server first.

Frequently Asked Questions

Do I need an MX record to send email?

You don't need an MX record to send outgoing email — your sending server uses SMTP directly to connect to recipient servers, which it finds via the recipient domain's MX records, not yours. However, you do need a valid MX record to receive email, including bounce notifications and warm-up replies. Without an MX record, bounce notifications (which you need for list hygiene) and warm-up reply emails cannot be delivered to your domain. ISPs also check for a valid MX record as part of sender verification — a domain with no MX record looks like an incomplete, potentially fraudulent setup.

What is MX record priority and how does it work?

MX priority is a numeric value that tells sending servers which mail server to try first when delivering to your domain. Lower numbers mean higher priority — so a server with priority 10 is tried before priority 20. Most senders use a single MX record, but publishing two provides failover: if the primary server is unavailable, sending servers automatically try the backup. Cloud mail providers (Google Workspace, Microsoft 365) automatically configure multiple MX records with appropriate priorities during setup. If you're self-hosting or using a less common mail provider, verify you have at least one valid MX record pointing to a functioning mail server.

How does a misconfigured MX record affect warm-up?

A misconfigured MX record means replies from your warm-up network cannot reach your mailbox — they'll bounce or be silently dropped. This eliminates a critical engagement signal: ISPs track not just that your warm-up emails generated replies, but that you received and processed those replies. Missing the reply delivery signal weakens your overall engagement profile. Additionally, any bounce notifications from failed warm-up sends won't reach you, making bounce rate tracking impossible. Always verify MX record functionality by sending a test email to your domain and confirming receipt before starting warm-up.

Related Terms

A Record

A DNS record that maps a domain name to an IPv4 address. A correctly configured A record is part of the complete DNS foundation required for email deliverability.

PTR Record (Pointer Record / Reverse DNS)

A DNS record mapping an IP address back to a hostname (reverse DNS). Many receiving servers reject email from IPs without a matching PTR record.

Email Infrastructure

The complete technical stack for sending and receiving email — servers, IPs, DNS, authentication protocols, and monitoring tools.

Forward DNS (DNS Lookup)

A standard DNS lookup that resolves a hostname to an IP address — a basic sanity check that receiving servers perform on every inbound SMTP connection.

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