When is it ok to deliver email without an MX record?
Michael Ko
Co-founder & CEO, Suped
Published 29 Jun 2025
Updated 15 Aug 2025
9 min read
When we talk about email, one of the foundational elements of its delivery system is the MX record. This critical piece of your Domain Name System (DNS) tells other mail servers where to send emails for your domain. Without it, incoming mail literally doesn't know where to go.
However, the question of whether email can be delivered, or more specifically, sent, without an MX record is a nuanced one. While an MX record is absolutely essential for a domain to receive emails, the rules for sending are slightly different. Let's delve into the specifics of when it's technically possible and, more importantly, when it's advisable.
The primary role of MX records
An MX record, or Mail Exchanger record, acts like a GPS for incoming email. When someone sends an email to you@yourdomain.com, the sending server first performs a DNS lookup to find the MX records associated with yourdomain.com. These records then point to the specific mail servers responsible for accepting that email. Without them, the sending server wouldn't know where to deliver the message, leading to email delivery failures.
Each MX record also includes a priority number, which helps establish an order if multiple mail servers are listed. A lower number indicates a higher priority. This setup provides redundancy, ensuring that if the primary mail server is unavailable, email can still be routed to a backup server. This is fundamental for consistent and reliable email receipt.
Properly configured MX records are a cornerstone of email deliverability, not just for receiving but also for establishing a legitimate presence on the internet. Incorrect or missing MX records can cause significant issues, making it seem as though your domain is not set up to handle email traffic, which can negatively impact how other servers perceive your domain.
Implicit MX and fallback to A records
While MX records are the standard for receiving email, there's a lesser-known rule defined in RFC 5321, the Simple Mail Transfer Protocol specification, known as the implicit MX rule. This rule states that if a domain has no MX records, the sending mail server should attempt to deliver the email directly to the host specified by the domain's A (Address) record or AAAA (IPv6 Address) record.
This fallback mechanism exists primarily for backwards compatibility with the early days of the internet, before MX records became standard. So, if a domain, like example.com, has an A record pointing to an IP address that also runs an SMTP server on port 25, it can technically receive mail. However, this is not a recommended practice for domains that intend to receive mail reliably.
The existence of an A record is indeed a prerequisite for email sending domains to function, even if they don't have MX records. You can learn more about this in our article on whether an A record is needed for sending domains. The general consensus in the email community is that while possible, relying on the implicit MX rule for receiving email can lead to inconsistent delivery and is not considered a robust setup for domains that prioritize email communication. Mailbox providers expect to see a properly configured MX record.
Standard email delivery
Expectation: Mail servers look for MX records to route inbound email messages.
Reliability: Highest chance of successful email delivery and receipt.
Setup: Requires specific MX records pointing to your mail servers.
Implicit MX fallback (A record delivery)
Expectation: If no MX records exist, some servers will attempt delivery to the domain's A/AAAA record.
Reliability: Less reliable, as many modern mail servers may not follow this fallback.
Setup: Domain must have an A or AAAA record and an SMTP server on port 25.
Implications for sender reputation and deliverability
While MX records are for inbound mail, the act of sending email itself doesn't directly require an MX record for the sending domain. Your Mail Transfer Agent (MTA) sends mail to the recipient's mail server. The recipient's server then queries DNS for the MX records of the recipient's domain, not your sending domain. So, in theory, you could send mail from a domain with no MX record.
However, this approach comes with significant drawbacks for email deliverability. Mailbox providers, like Google and Yahoo, perform numerous checks to determine the legitimacy and reputation of incoming mail. A missing MX record on a sending domain can be a red flag, signaling that the domain might not be a legitimate email sender or is poorly configured. This can lead to your emails being marked as spam, quarantined, or outright rejected.
Why MX records matter even for sending
Even if your domain doesn't plan to receive emails, having a valid MX record is crucial for receiving bounce notifications and DMARC reports. These reports provide vital feedback about your email sending performance and help identify potential issues that could be affecting your sender reputation. Without an MX record, this feedback loop is broken, leaving you blind to deliverability problems.
Therefore, while the technical possibility exists, it is generally considered bad practice to send email from a domain that lacks an MX record if you value deliverability. Sending from such a domain can negatively affect your sender reputation and lead to your emails being treated with suspicion by receiving servers. Understanding your email domain reputation is key to successful email programs.
Practical scenarios and null MX records
There are specific scenarios where a domain might intentionally not have MX records, or use a special type of record to explicitly state it doesn't receive email. For example, some domains are purely used for sending transactional emails (e.g., noreply@example.com) and are never expected to receive replies. In such cases, the domain owner might choose not to configure MX records. This is sometimes seen with vanity domains or those primarily serving a website with email handled elsewhere, often via generic email providers like Gmail or Outlook.
For domains that explicitly do not accept mail, it's best practice to publish a null MX record. This is a single MX record with a priority of 0 and a value of "." (a single dot), indicating that no mail servers accept mail for the domain. This signals to other mail servers that they should not attempt to deliver email to this domain, preventing unnecessary delivery attempts and potentially reducing spam backscatter.Using a null MX record is more robust than simply having no MX records at all, as it provides a clear, explicit instruction to the mail system.
Example of a null MX recordDNS
yourdomain.com. IN MX 0 .
Even with a null MX record, you can still send emails from such domains, provided your SPF and DKIM records are correctly configured. These authentication protocols verify the legitimacy of your sending domain, regardless of its MX configuration. However, remember that some validation services might still flag domains without traditional MX records as potentially invalid. Our article on why email validation services flag domains without MX records provides more detail on this behavior.
Understanding the email ecosystem's expectations
The common thinking is that if a domain has no MX record, it's not set up to receive mail. While that's largely true for practical purposes, it's also a bit more complex due to historical internet protocols. Mail servers are designed to look for an MX record first, but if one isn't found, they might fall back to trying to deliver to the domain's A record. This means an email could technically reach a server even without a specific MX designation, provided that server is configured to accept mail on port 25 for that domain's A record.
However, relying on this fallback is not ideal for reliable email delivery. Many modern mail servers (and the email infrastructure as a whole) expect proper MX records. If you're encountering delivery issues, especially with emails not reaching their intended recipients, checking the MX records is one of the first troubleshooting steps. This is covered in our guide on troubleshooting intermittent email delivery failures.
For domains primarily used for sending, such as those for marketing campaigns or transactional alerts, it's still advisable to have a well-defined MX strategy. This ensures that any bounce messages or DMARC reports have a designated recipient, providing valuable feedback that is crucial for maintaining good sender reputation. Neglecting MX records can lead to your emails being flagged by spam filters, or even ending up on a blocklist (or blacklist), which significantly hinders your email program's effectiveness.
Views from the trenches
Best practices
Always include an MX record on domains meant to receive email to ensure consistent delivery.
For sender-only domains, consider using a null MX record to explicitly signal no inbound mail.
Ensure proper SPF and DKIM authentication for all sending domains, regardless of MX records.
Monitor DMARC reports for domains without MX records to capture bounce and feedback data.
Common pitfalls
Assuming no MX record means emails can't be sent or received at all.
Ignoring the impact on sender reputation when sending from domains without MX records.
Failing to implement DMARC for sender-only domains, missing valuable deliverability insights.
Expecting all mail servers to respect the A record fallback, leading to unpredictable delivery.
Expert tips
Some spam filters will block emails from domains without MX records as a defensive measure.
Using a subdomain for sending allows you to isolate reputation risks from your main domain.
Even if you don't receive email at a domain, having a valid MX record can prevent some validation services from flagging it.
The fallback to A record is a legacy behavior; modern systems prioritize explicit MX records.
Expert view
Expert from Email Geeks says that if there's no MX record but an A record exists, you should attempt delivery to that A record.
2020-10-08 - Email Geeks
Marketer view
Marketer from Email Geeks says that while it's possible to deliver email to an A record, it's a strong indication that mail may not be a priority on that domain.
2020-10-08 - Email Geeks
Final thoughts on MX record necessity
While it's technically possible for an email to be delivered without an MX record, relying on this functionality is rarely advisable for domains that engage in active email communication. MX records are the bedrock of reliable email receipt and play a significant, albeit indirect, role in maintaining a healthy sender reputation. For domains primarily focused on sending, the absence of an MX record can lead to deliverability challenges and a lack of critical feedback from mailbox providers.
For optimal email deliverability, the best practice is to always have a properly configured MX record if your domain intends to receive emails. If a domain is purely for sending and never expects inbound mail, consider implementing a null MX record to provide clear signaling to other mail servers. Adhering to these best practices will help ensure your emails reach their intended recipients and your domain maintains a strong, trustworthy reputation in the eyes of the global email ecosystem.
Google and 
Yahoo, perform numerous checks to determine the legitimacy and reputation of incoming mail. A missing MX record on a sending domain can be a red flag, signaling that the domain might not be a legitimate email sender or is poorly configured. This can lead to your emails being marked as spam, quarantined, or outright rejected.
Gmail or 
Outlook.
