Does a missing MX record mean an email address is bad?
Michael Ko
Co-founder & CEO, Suped
Published 30 Jul 2025
Updated 19 Aug 2025
7 min read
When sending emails, one of the fundamental elements that dictate whether your message reaches its destination is the Domain Name System (DNS) configuration, specifically the MX record. It's common to encounter domains that appear to be missing this crucial record, leading to questions about the validity of associated email addresses. Does a missing MX record automatically deem an email address "bad" or undeliverable? Not always, but it certainly complicates things significantly and often points to underlying issues that can hinder successful email delivery.
An MX record, or Mail Exchange record, is a type of DNS record that specifies the mail server responsible for accepting email messages on behalf of a domain name. Think of it as the postal code for email, guiding messages to the correct destination server. Without it, mail servers don't know where to send incoming emails for that domain. While this might seem straightforward, the reality of email delivery, especially regarding missing MX records, can be more nuanced than it appears at first glance.
The role of MX records in email delivery
The core function of an MX record is to direct email. When an email sender's server (MTA) wants to send an email to user@example.com, it performs a DNS lookup for the MX record of "example.com." This record then provides the hostname (and sometimes a priority) of the mail server that should receive the email. The sending MTA then attempts to connect to that mail server to deliver the message.
Without an MX record, a domain essentially declares that it does not have a designated mail server to receive emails. This is a critical piece of information for any sending mail server. For businesses and individuals relying on email for communication, a properly configured MX record is non-negotiable for inbound mail flow. It's the primary way for other email servers to know where to deliver messages.
Checking for an MX record
You can easily check if a domain has an MX record using command-line tools like dig or nslookup. For instance, to check with dig, you would use a command similar to dig MX example.com. If no MX record is returned, or if only a Start of Authority (SOA) record is present, it indicates the absence of a designated mail server.
Example dig command to check MX recordbash
dig MX example.com
What the RFC says about missing MX records
While a missing MX record typically signifies that a domain is not set up to receive email, there's a technical nuance defined in RFC 5321 (Section 5.1). This standard specifies that if no MX records are found for a domain, the sending mail server should attempt to deliver the email directly to the host specified by the domain's A record (address record), treating it as an implicit MX record with a preference of 0. This means that, in theory, an email could still be delivered to a domain if it has an A record pointing to a mail server, even without an explicit MX record.
However, the reality often diverges from this theoretical fallback. Most modern mail servers and internet service providers (ISPs) strictly adhere to best practices for email routing and often ignore this RFC fallback. They prioritize explicit MX records for security, reliability, and anti-spam reasons. Relying on the A record fallback is generally considered a deprecated practice and can lead to significant deliverability issues. This is why many email validation services flag domains without MX records as invalid.
RFC vs. reality
RFC 5321 interpretation
The standard allows for a fallback to the domain's A record if no MX record is explicitly defined. This means that if example.com has an A record pointing to a server, an email could theoretically be sent to that server.
Modern mail server practice
Many major mail providers, including Google and Yahoo, often refuse to deliver mail to domains without explicit MX records. This is because a proper MX setup is a strong indicator of a domain's legitimate intent to receive mail. For more details on why mail servers refuse delivery, you can refer to discussions on the topic.
While an email address for a domain without an MX record isn't inherently "bad" in the sense of being malformed, it means that email delivery to it is highly improbable, if not impossible, in most practical scenarios. The address may exist, but it's like a house without a mailbox, making it effectively unreachable by traditional mail services.
Real-world impact on email deliverability
Sending emails to addresses on domains with missing MX records can lead to various negative consequences for your email program. Most commonly, these emails will result in a hard bounce, often with bounce reasons like "no MX record found" or "host not found." While a single bounce might not seem critical, a high bounce rate significantly impacts your sender reputation.
ISPs and email service providers (ESPs) monitor bounce rates as a key indicator of list quality and sending practices. High bounce rates can signal that you're sending to unmaintained or invalid addresses, which can lead to your emails being flagged as spam or even your sending IP being placed on a blacklist (or blocklist). This can affect your overall email deliverability to legitimate recipients.
Impact on sender reputation
Consequences of sending to non-MX domains
Hard bounces: Emails sent to domains without MX records will typically result in immediate and permanent delivery failures. This contributes to a higher overall bounce rate for your sending domain.
Sender reputation decline: A consistent pattern of sending to non-existent or unreachable domains signals poor list hygiene to ISPs. This can negatively impact your email domain reputation, leading to lower inbox placement rates even for valid addresses.
Blocklisting risk: If your bounce rates are excessively high, your sending IP or domain could be added to email blocklists, hindering future email campaigns. Understanding what happens when your domain is on a blacklist is crucial.
While a domain without an MX record might not technically mean the address is "bad" in terms of its syntax, it effectively means the address is unreachable for email purposes. Therefore, from a deliverability standpoint, you should treat such addresses as undeliverable and remove them from your active mailing lists to maintain good sender health.
Detecting and managing non-MX domains
To prevent deliverability issues, it's essential to actively identify and manage email addresses associated with domains lacking MX records. This involves proactive email validation and ongoing list hygiene practices.
Email validation services
Email validation services are designed to check the deliverability of email addresses before you send to them. A key part of their process involves performing DNS lookups, including checking for MX records. If a domain lacks an MX record, these services will typically flag the email address as invalid or undeliverable. This is an effective way to pre-emptively remove such addresses from your lists, as discussed in detail in our article on why email validation services flag domains without MX records.
Regularly cleaning your email lists helps maintain a healthy sender reputation and ensures your campaigns reach active, engaged recipients. This process should include removing addresses from domains that do not have proper MX records, as they will likely result in bounces.
Common bounce reasons
Bounce reason
Meaning
Action to take
No MX record
The domain has no specified mail servers.
Remove address from list.
Host not found
Similar to no MX, the domain itself or its mail server cannot be resolved. This is often linked to bounce messages due to missing MX.
Remove address from list.
DNS error
General DNS resolution issues, which could include problems with MX records.
Investigate DNS setup. Consider removing if persistent.
For domains that should have email capability but appear to be missing MX records, it's worth verifying their DNS configuration. Sometimes, it's a simple misconfiguration or a temporary DNS propagation issue. However, for domains that are genuinely not set up for email, continued attempts to send will only harm your deliverability metrics.
Proactive steps for list hygiene
Pre-send validation: Always validate email addresses before adding them to your list. This helps catch non-MX domains early.
Regular list cleaning: Implement a routine to remove bounced email addresses, especially hard bounces, from your active lists. This prevents repeated attempts to send to unreachable addresses.
Monitor deliverability metrics: Keep an eye on your bounce rates and other deliverability indicators to quickly identify and address any issues.
Views from the trenches
Best practices
Always validate email addresses upon collection to catch non-MX domains early in your acquisition process.
Implement a regular schedule for cleaning your email lists, focusing on hard bounces caused by missing MX records.
Use email authentication protocols like SPF and DMARC to improve overall sender reputation and deliverability.
Monitor your bounce rates closely and act quickly to remove problematic addresses from your sending lists.
Ensure your DNS records, especially MX records, are correctly configured and updated for all your sending domains.
Common pitfalls
Ignoring bounce notifications related to missing MX records, leading to a high bounce rate and reputation damage.
Failing to regularly clean email lists, resulting in continuous attempts to send to invalid or unreachable addresses.
Assuming that a domain without an MX record is merely a temporary issue without proper verification.
Relying on the RFC fallback to an A record, which most modern mail servers do not honor for email delivery.
Not understanding the difference between a temporary DNS issue and a permanent lack of MX record configuration.
Expert tips
If a domain has no MX record but does have an A record, some legacy systems might still attempt delivery, but modern systems will almost certainly hard bounce.
A missing MX record isn't necessarily a bad email *address* syntactically, but it makes it undeliverable. It's best to treat it as such for list hygiene.
Using a reliable third-party email validation service is your best bet to accurately identify domains without MX records before sending.
High bounce rates from missing MX records can trigger blocklists, even if your content is legitimate.
Consider segmenting your list based on validation results, suppressing undeliverable addresses from your primary sends.
Expert view
Expert from Email Geeks says: If a domain has no MX record, it often indicates an issue, but it's not a definitive sign of a bad email address.
2019-09-27 - Email Geeks
Marketer view
Marketer from Email Geeks says: Using an email verification service can provide additional insight into whether an email domain is valid for sign-ups.
2019-09-27 - Email Geeks
Summary and best practices
In summary, while the absence of an MX record doesn't necessarily mean an email address is syntactically malformed, it means that email delivery to that domain is highly unlikely to succeed. Modern mail servers and anti-spam systems primarily rely on explicit MX records to route email correctly, and without them, messages are almost certainly to bounce. This can severely impact your sender reputation and overall deliverability.
Therefore, from a practical email marketing and deliverability perspective, any email address associated with a domain lacking an MX record should be treated as undeliverable. Proactive email validation and rigorous list hygiene are crucial steps to identify and remove such addresses, ensuring your email campaigns remain effective and your sender reputation stays healthy.
Google and 
Yahoo, often refuse to deliver mail to domains without explicit MX records. This is because a proper MX setup is a strong indicator of a domain's legitimate intent to receive mail. For more details on why mail servers refuse delivery, you can refer to discussions on the topic.
