When is it ok to deliver email without an MX record?

Key findings

• Default expectation: MX records are the standard DNS record for guiding incoming email to the correct mail server. Most email systems expect them to be present.
• A record fallback: If a domain lacks an MX record, sending mail servers may attempt to deliver email to the domain's A (IPv4) or AAAA (IPv6) record. This is a behavior rooted in older internet protocols.
• Technical possibility: While technically possible, delivering email directly to an A record is not a recommended or reliable practice for modern email systems.
• Indication of non-mail domain: The absence of an MX record often indicates that a domain is not configured or intended to receive email, serving primarily for web hosting or other purposes.

Key considerations

• Deliverability risk: Sending to domains without proper MX records significantly increases the risk of emails being rejected or lost. It can negatively impact your overall email deliverability.
• Bounce and complaint processing: Without an MX record, your system may not receive critical bounce notifications or complaint feedback from recipient mail servers, hindering your ability to maintain a clean list.
• Domain validation services: Many email validation services will flag domains without MX records as invalid, even if an A record exists, because they indicate a lack of proper email infrastructure. Explore why email validation services flag domains without MX records.
• Understanding core DNS: A clear understanding of how MX records work within DNS is fundamental for effective email delivery, alongside other records like A, AAAA, SPF, and DKIM.

Key opinions

• A record acceptance: Many marketers acknowledge that if an MX record is absent, emails can still technically be delivered to the domain's A record, though this is often seen as a fallback.
• Strong indicator of non-mail: The lack of an MX record is generally perceived as a strong indication that the domain is not intended to handle email, but rather primarily for web services or other purposes.
• Common for small businesses: It's common for small businesses or brochure domains to use free email services like Gmail, meaning their domain won't have an MX record pointing to its own mail server.
• Shared hosting defaults: Some shared hosting providers might not configure MX records by default, especially if email service isn't the primary focus for the domain.
• Practicality over technical setup: For many, the convenience of using an existing free email address (e.g., Gmail) outweighs the perceived complexity of setting up domain-specific email.

Key considerations

• Suspicious indicators: While not always the case, some marketers view domains without MX records as potentially suspicious, especially if they resemble spam sites.
• User preference: Users may prefer the interface and familiarity of services like Gmail, or have their existing email address already widely advertised (on vans, business cards, etc.).
• Mobile access challenges: Email from standard shared hosting may lack modern features like ActiveSync, making mobile access cumbersome and pushing users to third-party services. This can lead to issues that require troubleshooting email delivery failures.
• Understanding domain setup: For successful campaigns, it is important to understand what happens if a domain lacks MX records, particularly when considering whether an email address is valid for contact.

Key opinions

• Legacy fallback: Experts confirm that the fallback to an A record for email delivery is a historical artifact, primarily for backward compatibility with the internet's early days before MX records were standard.
• AAAA record limitations: Unlike A records, if a domain only has an AAAA record (IPv6) and no MX or A record, email delivery is highly likely to fail. AAAA records are newer than MX, so domains using them are expected to also have proper MX records.
• RFC compliance: Modern email RFCs and systems implicitly, and often explicitly, expect the presence of MX records for correct mail routing and adherence to best practices.
• Clear signal: The absence of an MX record serves as a clear signal to sending mail servers that the domain is likely not configured to receive email, influencing delivery decisions.

Key considerations

• Unreliable delivery: Relying on the A record fallback is unreliable and should be avoided for legitimate email traffic, as it can lead to inconsistent delivery and problems with bounce processing.
• Impact on sender reputation: Sending emails to domains without MX records can flag your sending IP or domain as suspicious to receiving mail servers, potentially leading to blocklist inclusion or spam folder placement.
• Comprehensive DNS setup: Beyond MX and A records, other DNS records like PTR are essential for robust email deliverability. Understanding what PTR records are and their role is important.
• Compliance and best practices: While some edge cases allow delivery without MX, adhering to established DNS and email sending best practices, including proper MX records, is critical for long-term deliverability and avoiding issues like improperly configured DNS.

Key findings

• SMTP instruction: Documentation confirms that the main purpose of an MX record is to provide explicit instructions to sending mail servers about where to deliver emails for a domain via SMTP.
• Undelivered emails: Without an MX record, sending servers typically lack the necessary information to route messages correctly, leading to emails being undelivered.
• Functional email requirement: Many resources state that an MX record is absolutely necessary for a domain to have a functional, custom business email address.
• DNS record type: MX records are a specific type of DNS record, crucial for directing email traffic within the broader internet infrastructure.

Key considerations

• Bounce and complaint feedback: As per documentation (e.g., from AWS), an MX record is required for a domain to receive bounce and complaint notifications, which are vital for sender hygiene.
• Domain verification: Email service providers often mandate proper MX records for domain verification processes before they allow email sending from that domain.
• RFC compliance vs. practice: While RFCs outline standard behavior, practical implementations by various mail transfer agents (MTAs) might have some leniency, allowing for A record fallbacks, particularly for very old setups. More on this can be found in what RFC 5322 says versus what actually works.
• Holistic authentication: MX records are one part of a comprehensive DNS setup that includes SPF, DKIM, and DMARC, all of which are essential for robust email authentication. See a simple guide to DMARC, SPF, and DKIM.