Are A records for return-path domains necessary for email deliverability or required by RFC standards?
Michael Ko
Co-founder & CEO, Suped
Published 18 Jul 2025
Updated 12 Oct 2025
6 min read
When delving into the intricacies of email deliverability, one question that often arises is whether A records for return-path domains are truly necessary. We frequently encounter discussions and observe varying configurations among email service providers (ESPs), leading to confusion about what constitutes a best practice versus a strict requirement.
The return-path, also known as the envelope sender or MAIL FROM address, is crucial because it's where bounce messages are sent. It's often different from the From domain (RFC 5322.From) that recipients see in their email client. But does the domain used in this return-path require an A record for optimal delivery or to comply with standards?
This article aims to clarify the role of A records for return-path domains, examining both RFC standards and their practical impact on email deliverability.
RFC standards and the return-path domain
The RFCs, particularly RFC 5321 (Simple Mail Transfer Protocol), primarily focus on the deliverability of the return-path address itself, meaning that a Mail Exchange (MX) record must be present for the domain to accept incoming mail. This is essential for handling bounce messages and other mail server communications, ensuring that error notifications can return to the sender.
However, RFC 5321 does not explicitly mandate an A record for the return-path domain. An A record maps a domain name to an IPv4 address, which is typically used for web hosting or direct IP-based connections. For email delivery, the MX record directs mail to the appropriate server, rather than the A record.
SPF (Sender Policy Framework), defined in RFC 7208, directly leverages the Return-Path domain. An SPF record, which is a TXT record, specifies which IP addresses are authorized to send email on behalf of that domain. The receiving server performs an SPF check against the Return-Path domain to verify the sender's legitimacy. While an A record for the Return-Path domain isn't a direct requirement, a properly configured SPF record for it is vital for authentication.
Practical deliverability considerations
Despite RFCs not explicitly requiring an A record for the return-path domain, many senders and ESPs implement them. This practice often stems from historical configurations where mail servers and web servers shared the same IP, or simply from copying existing setups without full understanding. Some people believe that having an A record, even if not directly used for mail routing, might positively influence spam filters.
While an A record on the return-path domain itself isn't a primary deliverability factor, the DNS setup of the actual sending IP address is critical. This includes a valid A record for the hostname that resolves to the sending IP, and a matching PTR record (reverse DNS) that points back to the hostname. This forward-confirmed reverse DNS (FCrDNS) is a common spam prevention technique. While not about the return-path domain's A record directly, a missing A record for the primary sending domain can lead to domain not found errors.
One edge case I've observed involves a client whose domain's A record (not the sending IP) pointed to a web hosting IP that was listed on SpamHaus. iCloud began issuing local policy block messages. While the A record wasn't for the sending IP, its association with the sending domain via other DNS records seemed to trigger a blocklist (or blacklist) check. This highlights that while not strictly required, having clean A records for any domain associated with your email sending is a good practice to avoid unforeseen deliverability issues.
RFC perspective
RFCs do not mandate an A record for the Return-Path domain. The primary requirement is an MX record to facilitate the delivery of bounce messages back to the sender.
Impact on deliverability
Direct impact is minimal; the core deliverability relies on the sending IP's PTR and A records, and the authentication protocols like SPF, DKIM, and DMARC. However, some receiving systems might check A records for associated domains, so a bad record could cause issues.
Different ESP configurations
Observing how different ESPs configure their DNS for return-path domains reveals a range of valid engineering choices. This confirms that there's no single, universally adopted standard beyond the RFCs that demands an A record for the return-path domain itself.
Mailchimp
Mailchimp often uses a setup where the return-path domain, like mail19.mailchimp.com, also serves as the reverse DNS (PTR record) for the connecting IP. In these cases, the domain will also have an A record that points back to the sending IP, creating a full circle DNS configuration.
SparkPost
With SparkPost, a return-path domain like bounce.asana.com might be a CNAME to sparkpostmail.com. In this scenario, sparkpostmail.com itself may not have an A record. The important DNS loop (A and PTR) would then reside with the actual MTA hostname, such as mta175d.sparkpostmail.com, which does have the full circle DNS trip.
Amazon SES
Amazon SES often uses generic return-path domains like amazonses.com. While amazonses.com may have A records, these records typically point to their CDN infrastructure (like cloudfront) rather than directly back to their sending IPs. In such cases, there isn't a full circle DNS on the return-path domain itself, but the overall deliverability is still high due to their infrastructure and reputation.
ExactTarget / Pardot
These platforms might use return-path domains like bounce.s7.exacttarget.com. While such a domain may have an A record, it often points to a different server or IP address than the actual sending IP. This setup is perfectly valid and demonstrates that an A record on the return-path domain isn't necessarily tied to the sending infrastructure in a direct one-to-one relationship for deliverability purposes.
These examples highlight that a strict requirement for an A record on the return-path domain is not universally enforced or necessary. What truly matters is that the domain is properly configured for SPF validation and can receive bounce messages via its MX records.
The actual DNS records that matter
When setting up your email infrastructure, the critical DNS records for deliverability revolve around the actual sending IP and its associated hostname, rather than just the return-path domain itself. Ensuring your sending IP has proper reverse DNS (PTR) that matches its forward DNS (A record) is generally more impactful.
Furthermore, a robust SPF record on your return-path domain is non-negotiable for proper email authentication. Here's a basic example of an SPF record you might see:
While adding an A record to your return-path domain will likely do no harm, and some ESPs do it for their own engineering reasons, it's not a direct RFC requirement nor a primary factor in getting your emails to the inbox. Focus your efforts on the core authentication mechanisms and maintaining a positive sender reputation.
DNS record types for email
MX Record: Specifies the mail servers responsible for accepting email messages on behalf of a domain. Essential for the return-path domain to receive bounces.
A Record: Maps a hostname to an IPv4 address. Critical for the actual sending IP's hostname, but not strictly required for the return-path domain itself.
PTR Record (Reverse DNS): Maps an IP address back to a hostname. Essential for sender reputation checks, as many receiving servers verify FCrDNS.
TXT Record (SPF): Used for SPF authentication, specifying authorized sending IPs for a domain, including the return-path domain. Crucial for deliverability.
Views from the trenches
Best practices
Ensure your return-path domain has a valid MX record for bounce processing.
Always publish a comprehensive SPF record for your return-path domain.
Maintain correct forward and reverse DNS (PTR) for all sending IPs.
Align your DMARC records with both your From and Return-Path domains.
Regularly monitor your domain's reputation and avoid blocklists.
Common pitfalls
Assuming an A record is required for the return-path domain due to legacy setups.
Overlooking the importance of MX records for bounce handling.
Neglecting to configure proper PTR records for sending IPs, impacting deliverability.
Ignoring SPF alignment for the Return-Path domain, leading to authentication failures.
Not having a strategy for
Expert tips
If in doubt about A records for your return-path, it usually doesn't hurt to add one if it resolves to a clean IP.
Prioritize a strong FCrDNS configuration for your sending IPs over an A record on the return-path domain.
Focus on robust email authentication (SPF, DKIM, DMARC) for all sending domains.
Use blocklist (or blacklist) monitoring tools to detect and address any IP or domain listings promptly.
Regularly review your DNS settings to ensure they are consistent and accurate for all email streams.
Expert view
Expert from Email Geeks says that there's no specific RFC requirement for an A record on the return-path domain if an MX record is present. The deliverability only implicitly relies on the email address being deliverable.
2019-09-17 - Email Geeks
Marketer view
Marketer from Email Geeks says that many senders do set up A records for return-path domains, which gives the impression it's standard, even if RFCs don't require it. This is often due to copying existing configurations.
2019-09-17 - Email Geeks
Key takeaways for your email DNS strategy
In summary, an A record for your return-path domain is not required by RFC standards for email delivery. The critical RFC requirement for the return-path (MAIL FROM) domain is the presence of an MX record, enabling it to receive bounce messages and facilitate SPF authentication.
While some ESPs choose to configure A records for their return-path domains, these are typically engineering decisions rather than strict deliverability mandates. The primary DNS considerations for email deliverability lie with the sending IP address, including proper forward and reverse DNS resolution (A and PTR records), and strong authentication protocols like SPF, DKIM, and DMARC. Focusing on these foundational elements will yield the most significant improvements in your email deliverability rates.
Are A records for return-path domains necessary for email deliverability or required by RFC standards? - Technical - Email deliverability - Knowledge base - Suped
iCloud began issuing local policy block messages. While the A record wasn't for the sending IP, its association with the sending domain via other DNS records seemed to trigger a blocklist (or blacklist) check. This highlights that while not strictly required, having clean A records for any domain associated with your email sending is a good practice to avoid unforeseen deliverability issues.
Mailchimp often uses a setup where the return-path domain, like mail19.mailchimp.com, also serves as the reverse DNS (PTR record) for the connecting IP. In these cases, the domain will also have an A record that points back to the sending IP, creating a full circle DNS configuration.
SparkPost, a return-path domain like bounce.asana.com might be a CNAME to sparkpostmail.com. In this scenario, sparkpostmail.com itself may not have an A record. The important DNS loop (A and PTR) would then reside with the actual MTA hostname, such as mta175d.sparkpostmail.com, which does have the full circle DNS trip.
Amazon SES often uses generic return-path domains like amazonses.com. While amazonses.com may have A records, these records typically point to their CDN infrastructure (like cloudfront) rather than directly back to their sending IPs. In such cases, there isn't a full circle DNS on the return-path domain itself, but the overall deliverability is still high due to their infrastructure and reputation.
