Summary
A missing MX record generally means an email address is effectively 'bad' or undeliverable for receiving mail. MX records are crucial DNS entries that tell other mail servers where to send email for a domain. Without them, email servers cannot locate the correct destination, leading to delivery failures and hard bounces. While there's a technical fallback to an A record according to RFC 5321, in practice, email marketing experts and major email providers universally agree that the absence of an MX record indicates an email address is non-functional for inbound mail. Sending to such an address will not incur deliverability penalties, as no one is listening to receive, but the email will not be delivered.
Key findings
- Essential for Delivery: MX (Mail Exchange) records are fundamental for email delivery, directing mail servers to the correct destination for incoming email. Without them, email cannot be routed to the recipient's domain.
- Undeliverable Addresses: If a domain lacks an MX record, any email addresses associated with that domain are effectively unable to receive mail, rendering them non-functional for inbound communication.
- Hard Bounces Expected: Emails sent to domains without a designated MX record will invariably result in hard bounces because there is no mail server specified to accept the incoming messages, indicating a permanent delivery failure.
- Indication of Bad Addresses: From a practical email marketing standpoint, a missing MX record is a clear signal that an email address is 'bad,' meaning it cannot receive messages and should not be included in active mailing lists.
Key considerations
- Use Verification Tools: Tools such as check-mail.org can help determine if a domain is valid for email sign-ups, identifying missing MX records early in the process.
- Inbound vs. Outbound Impact: A missing MX record primarily prevents a domain from receiving email. While it doesn't stop an email address from sending mail, an address unable to receive is generally considered non-functional for two-way communication.
- Broader List Issues: A domain lacking an MX record can signify more extensive problems beyond just deliverability, indicating potential issues with overall list hygiene or domain setup.
- RFC vs. Practicality: While RFC 5321 permits a fallback to an A record if no MX record exists, in real-world email marketing, a missing MX record is a strong indicator of an undeliverable address and should be treated as such.
What email marketers say
13 marketer opinions
An email address is generally considered non-functional for receiving messages if its domain lacks an MX (Mail Exchange) record. Without these crucial DNS entries, mail servers are unable to identify where to deliver incoming emails, leading to immediate hard bounces. This consensus among email marketing professionals and major providers highlights that a missing MX record is a strong indicator of an undeliverable address. Though RFC 5321 outlines a fallback mechanism to an A record, practical application dictates that such an address cannot effectively receive mail. Consequently, while attempting to send an email to a domain without an MX record won't typically harm a sender's reputation, since no server is listening, the message itself will fail to be delivered.
Key opinions
- Vital for Reception: MX records are essential for any domain to receive emails, providing the necessary routing instructions for mail servers.
- Undeliverable Status: An email address on a domain without an MX record is deemed undeliverable, as there is no designated server to accept incoming mail.
- Guaranteed Bounces: Emails directed to such addresses will consistently result in hard bounces, signaling a permanent delivery failure due to the absence of a mail server.
- Indicator of Invalidity: For email hygiene purposes, a missing MX record is a clear signal that an email address is invalid for communication, making it unsuitable for active mailing lists.
Key considerations
- Leverage Verification Tools: Employing email verification services or specific tools like check-mail.org can help identify domains lacking MX records, allowing for proactive list cleaning.
- Impact on Inbound Mail: The primary effect of a missing MX record is on the ability to receive mail, it does not, however, prevent an address from sending emails.
- Potential for Broader Issues: Beyond just deliverability, a domain without an MX record may indicate underlying configuration problems or general neglect, potentially pointing to other list quality concerns.
- Practicality Over Protocol: Despite the theoretical allowance for an A record fallback in RFCs, the practical reality in email marketing is that a missing MX record almost always means an address is unusable for receiving email.
Marketer view
Email marketer from Email Geeks shares check-mail.org as a tool to help determine if an email domain is valid for sign-ups.
25 Jan 2022 - Email Geeks
Marketer view
Email marketer from Email Geeks explains that if Google's resolvers don't find an MX record, it's likely not there, although records can be deleted. He also details how to force dig to specific resolvers and notes that a missing MX record can indicate other list issues.
27 Jan 2025 - Email Geeks
What the experts say
2 expert opinions
A missing MX record renders an email address effectively undeliverable, as it prevents mail servers from identifying the correct destination for incoming messages. Without this critical DNS entry, emails sent to addresses within that domain cannot be delivered, consistently resulting in bounces. This fundamental requirement for mail routing means that any email address residing on a domain without a properly configured MX record is essentially non-functional for receiving communications.
Key opinions
- Core Routing Function: MX records are fundamental DNS entries that direct mail servers to the correct destination for emails, enabling proper routing to a domain's mail server.
- Prevents Delivery: The absence of an MX record means external mail servers cannot locate where to deliver email for that domain, making any addresses within it unable to receive messages.
- Non-Functional Addresses: An email address is considered non-functional for receiving mail if its domain lacks an MX record, as communication cannot be successfully routed to it.
Key considerations
- Identify Undeliverable Mailboxes: Confirming the presence of an MX record is a fundamental step in pre-validating email addresses, ensuring they belong to domains capable of receiving mail and reducing delivery failures.
- Immediate Bounce Risk: Sending to an email address on a domain without an MX record will result in an immediate hard bounce, as there is no server to accept the message, signaling a permanent delivery failure.
- Reflects Domain Activity: The absence of an MX record often indicates that a domain is not actively set up for email communication, suggesting it might be defunct or improperly configured, which affects overall list quality.
Expert view
Expert from Spam Resource explains that an MX record points to a domain's mail server. Without one, mail servers cannot locate where to deliver email for that domain, meaning emails sent to addresses within that domain cannot be delivered, effectively rendering those addresses undeliverable.
1 Apr 2024 - Spam Resource
Expert view
Expert from Word to the Wise explains that an MX record is essential as it specifies which mail server accepts email for a given domain. Without a valid MX record, it is impossible to send email to any address within that domain, making such email addresses undeliverable.
27 Sep 2021 - Word to the Wise
What the documentation says
5 technical articles
Across the board, documentation from leading tech companies and email providers confirms that a missing MX record unequivocally means an email address cannot receive mail. This critical DNS entry is essential for directing incoming messages, and without it, email servers are unable to locate the correct destination, leading to consistent delivery failures and hard bounces for any address on that domain. Therefore, an email address on a domain without an MX record is effectively non-functional for inbound communication.
Key findings
- Unanimous Consensus on Impact: Leading providers and technical documentation consistently agree that a missing MX record prevents email delivery to that domain, rendering associated email addresses unable to receive mail.
- Blocking Inbound Mailflow: Without an MX record, mail servers lack the necessary instructions to route incoming email, effectively blocking any messages from reaching addresses on that domain.
- Direct Cause of Bounces: Emails sent to domains without an MX record will inevitably result in hard bounces, indicating a permanent failure to deliver due to the absence of a designated mail server.
- Signifier of Unusable Addresses: From a practical standpoint, an email address on a domain lacking an MX record is considered unusable for receiving inbound communication, making it a 'bad' address for marketing purposes.
Key considerations
- Fundamental for Receivability: A correctly configured MX record is not merely a technical detail, but a fundamental requirement for any email address to be capable of receiving messages, making it crucial for effective communication.
- Essential for List Hygiene: Identifying and removing email addresses associated with domains lacking MX records is a vital step in maintaining a clean and high-performing email list, reducing bounce rates and improving sender reputation.
- Indicates Domain Status: The absence of an MX record often signifies that a domain is not set up to receive email, possibly indicating it is inactive, abandoned, or improperly configured, which impacts overall list quality.
- Critical for Deliverability: When building an email list, verifying the presence of MX records is a foundational check to ensure that the collected addresses belong to domains where email can actually be delivered.
Technical article
Documentation from Cloudflare explains that without MX records, email servers cannot locate the correct destination to deliver email, effectively making an email address on such a domain unable to receive mail.
8 Mar 2025 - Cloudflare
Technical article
Documentation from Google Workspace explains that MX (Mail Exchange) records direct a domain's email to their servers, and without correct MX records, email won't be delivered to that domain, making any addresses on it non-functional for inbound mail.
3 May 2022 - Google Workspace Admin Help
Does having an MX record on the from domain improve email deliverability?
How do MX records impact email bounces and sender reputation?
How does a missing DKIM DNS TXT record affect email deliverability?
Is it bad for email deliverability to send from a non-existent email address?
Is it bad practice to send email from a domain without an MX record?
When is it ok to deliver email without an MX record?
