Is an email deliverable if its domain has an A record but no MX record?
Michael Ko
Co-founder & CEO, Suped
Published 6 Aug 2025
Updated 18 Aug 2025
6 min read
When setting up email for your domain, you typically configure Mail Exchange (MX) records. These specialized DNS records tell other mail servers where to send emails addressed to your domain. They act like signposts, directing incoming mail to the correct server that can accept and store your messages.
However, sometimes domains are configured with only an A record, which maps a domain name to an IP address, but no MX record. This leads to a common question: Can an email still be delivered to a domain that has an A record but lacks an MX record? The answer is nuanced, rooted in historical email protocols and modern deliverability expectations.
While technically possible according to older specifications, relying solely on an A record for email delivery in today's landscape is highly impractical and will almost certainly lead to deliverability issues.
The standard email delivery process
The standard process for sending an email begins with the sending Mail Transfer Agent (MTA) performing a DNS lookup for the recipient's domain. Its primary goal is to find an MX record. These records specify the mail servers responsible for receiving email for a domain, along with their preference (priority) values.
An MX record points to a hostname, which in turn resolves to an IP address via an A record. For example, an MX record for example.com might point to mail.example.com, and then mail.example.com would have an A record pointing to its server's IP address. This two-step process ensures that mail can be routed even if the mail server's IP changes.
Without an MX record, the sending server lacks the explicit instructions needed to route the email. This is where the concept of an A record fallback comes into play. You can read more about A records and their role in email on our knowledge base.
When an A record steps in for email delivery
According to RFC 5321, the governing standard for email transfer, 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 record. This means that, in theory, an email could still reach its destination even without an MX record, provided the A record points to a server configured to accept mail on port 25.
While this fallback mechanism is part of the RFC, it is rarely implemented or relied upon in modern email systems. The vast majority of current email infrastructure expects and requires a properly configured MX record. Major email providers like Google and Microsoft strictly adhere to MX record lookups as the primary method for routing emails. If they do not find an MX record, they will likely return a bounce message indicating that the domain does not accept email.
The risks of no MX record
Even if an older mail server attempts to deliver to an A record, there's no guarantee the server at that IP address is set up to receive email. It might be a web server, a game server, or any other type of host not configured for SMTP.
Deliverability: Emails are highly likely to bounce or be rejected by recipient mail servers. Many modern servers treat the absence of an MX record as a strong indicator of an invalid or misconfigured domain.
Spam filters: Email sent to or from domains without MX records can be flagged as suspicious. This can negatively impact your sender reputation, leading to lower inbox placement rates.
Standards: While RFC 5321 permits it, best practices and common implementations overwhelmingly favor MX records for email delivery. You can review the RFC 5321 specifications directly.
If you are struggling with email validation services flagging domains without MX records as invalid, we've explored whether emails can still be delivered in a separate article.
Checking for MX and A recordsbash
dig MX example.com
dig A example.com
Why relying on A records is risky for email
Relying on an A record for email delivery, even if technically permitted by an RFC, is a significant risk to your email deliverability. Mail servers, especially those belonging to major ISPs, prioritize security and legitimate email practices. A missing MX record signals potential misconfiguration or, worse, an attempt to bypass standard email routing, which can trigger spam filters and even lead to your domain or IP being put on an email blocklist (or blacklist).
It is bad practice to send email from a domain without an MX record because it signals a lack of proper setup, which can degrade your sender reputation. A poor sender reputation will cause your emails to land in spam folders or be rejected outright.
MX record present
Standard routing: Mail servers easily find the designated mail handler for the domain.
High deliverability: Emails are delivered reliably to the recipient's inbox, assuming other factors are in order.
Positive reputation: Proper configuration enhances your domain's credibility with receiving servers.
MX record missing
Unreliable routing: Sending servers may attempt fallback to A record, but often fail or reject.
Low deliverability: High likelihood of bounces, rejections, or delivery to spam folders.
Negative reputation: Signals poor domain setup, which can damage sender reputation and trigger blocklisting.
This highlights why, for any domain intending to receive email, a properly configured MX record is not just recommended, but effectively mandatory for reliable deliverability. When your domain is put on an email blocklist (or blacklist), it can severely impact your ability to reach inboxes. Understanding how email blacklists work is key to avoiding these pitfalls.
Ensuring optimal email deliverability
For optimal email deliverability, always ensure your domain has correctly configured MX records. This is the fundamental step for telling the world where to send your emails. Without them, you are leaving deliverability to chance, and in email, chance usually means the spam folder or outright rejection.
Beyond MX records, other DNS records like SPF, DKIM, and DMARC are vital for authenticating your emails and protecting your domain from spoofing and phishing. These records build trust with receiving mail servers and are critical for modern email security and deliverability. We cover a simple guide to DMARC, SPF, and DKIM in our guides.
Key takeaways for reliable email
Always use MX records: Properly configured MX records are the bedrock of reliable email delivery.
Monitor your DNS: Regularly check your DNS records to ensure they are correct and haven't been tampered with or expired.
Implement authentication: Set up SPF, DKIM, and DMARC to authenticate your sending domain and improve trust.
By following these best practices, you can significantly improve your email deliverability rates and ensure your messages consistently reach their intended recipients. To understand more about the importance of PTR records alongside A and MX records, see our dedicated article.
Views from the trenches
Best practices
Always include MX records for domains that are expected to receive email.
Utilize SPF, DKIM, and DMARC for comprehensive email authentication.
Regularly monitor your domain's DNS records for correct configuration and changes.
Ensure your mail servers are properly configured to accept incoming connections.
Common pitfalls
Assuming an A record fallback is a reliable email delivery method in modern systems.
Neglecting to configure MX records after setting up a new email service.
Not regularly checking DNS records, leading to outdated or incorrect entries.
Ignoring bounce messages that indicate MX record issues.
Expert tips
Consider a 'null MX record' (priority 0, target '.') for domains that should never receive email, explicitly indicating no mail service. This is particularly useful for domains used only for sending, preventing backscatter.
Be aware that some legacy systems might still attempt A record fallback, but modern, large ISPs will not.
For transactional emails, having a robust MX setup for reply-to addresses helps maintain sender reputation by allowing bounces to be processed.
Use DNS checking tools to verify your MX records and other DNS settings after any changes.
Marketer view
Marketer from Email Geeks says they verify emails for validity before passing them to sales, noting that an MX record without an answer typically means a spelling error or no response.
2023-09-15 - Email Geeks
Marketer view
Marketer from Email Geeks says that if an A record is present, a properly performing Mail Transfer Agent (MTA) should attempt to send to it as a default fallback option.
2023-10-20 - Email Geeks
The crucial role of MX records
While the internet's original email specifications allowed for a fallback to an A record if no MX record was present, this is largely a theoretical possibility in today's email environment. Modern email systems, especially those run by major providers, strictly rely on MX records for routing mail.
For reliable email deliverability, an MX record is not just optional but a fundamental requirement. Its absence will almost certainly lead to emails bouncing, being flagged as spam, or simply failing to reach their intended recipients, ultimately harming your sender reputation and deliverability.
Google and 
Microsoft strictly adhere to MX record lookups as the primary method for routing emails. If they do not find an MX record, they will likely return a bounce message indicating that the domain does not accept email.
