Summary
An A record, or Address record, is a fundamental DNS record that maps a domain name to an IPv4 address. For email sending domains, the necessity of an A record depends on which part of the email header you are referring to, specifically the MAIL FROM (envelope sender) versus the Header From (visible sender). While an A record is generally considered essential for the MAIL FROM domain to prevent rejections, it's highly recommended as a best practice for the Header From domain, even if not strictly required for delivery in all instances. Its presence signals legitimacy and transparency, contributing to overall email deliverability and sender reputation.
Key findings
- Mail From importance: An A record for the MAIL FROM domain (also known as the envelope sender or return-path domain) is crucial. Mail Transfer Agents (MTAs) often reject emails if this domain lacks an A record, as it appears suspicious.
- Header from recommendation: While not as critical as the MAIL FROM, having an A record for the Header From (visible sender) domain is strongly recommended. It contributes to the perception of a legitimate sending domain and improves trust.
- General suspicion: Any domain used in email sending that lacks an A record is generally viewed as suspicious by receiving servers, potentially leading to deliverability issues. This highlights the importance of proper DNS configuration for your sending domain.
- DNS resolution: The A record is a fundamental requirement for DNS servers to resolve a domain name to an IP address. Without it, the domain cannot be properly located on the internet, which directly impacts email deliverability. For more information, consider reading this guide on DNS and email.
- Website alignment: A common best practice, especially for the Header From domain, is to have its A record point to an IP address associated with the sender's website. This provides a web presence that helps identify the sender and reinforces legitimacy.
Key considerations
- Subdomain configuration: When using subdomains for sending, ensure each subdomain that acts as a MAIL FROM or Header From domain has its appropriate A record configured. This also applies to other necessary records like SPF, DKIM, and DMARC.
- Brand consistency: Aligning your sending domain's A record with your main website's IP or a relevant web presence (even a redirect page) can bolster brand identity and trust, particularly if recipients manually check the domain.
- Monitoring DNS: Regularly verify your DNS records, including A records, to ensure they are correctly configured and resolve properly. Errors can lead to significant deliverability issues and potentially cause domains to be placed on blocklists.
- Distinction from MX: An A record points a domain to an IP address, while an MX record specifies mail servers for receiving email. Although distinct, MX records rely on A records to resolve the IP addresses of the mail servers they point to. For more context, see this discussion on MX record function.
What email marketers say
Email marketers often discuss the practical implications of DNS records on campaign performance and reputation. Many agree that while the technical necessity of an A record varies between the MAIL FROM and Header From domains, the best practice leans towards having A records for all sending domains to ensure legitimacy and avoid suspicion from receiving servers. This proactive approach helps in maintaining a strong sender reputation, which is vital for inbox placement.
Key opinions
- Suspicion without A record: Many marketers observe that any domain lacking an A record can appear suspicious to receiving MTAs, potentially leading to mail rejections or increased spam filtering. This is a common sentiment in the community.
- Best practice for header from: It is considered a standard best practice, often followed by large ESPs, to include an A record for the subdomain used in the RFC 5322 From header (Header From). This A record typically points to the client's main website IP address.
- Mail from criticality: There's a strong consensus that an A record is essential for the MAIL FROM domain, as its absence can lead to outright rejections by MTAs. This is a more critical requirement compared to the Header From domain.
- Transparency and legitimacy: Having an A record for domains used in email communication improves transparency and signals legitimacy. This positive signal helps in establishing a trusted sender identity, which is crucial for deliverability.
- Web presence for sender ID: If an A record exists for the Header From domain, it should ideally point to a web presence (like a redirect to the main site) that identifies the sender. This is because recipients or systems might look up the A record to verify the sender's identity.
Key considerations
- Avoiding rejections: To minimize the risk of email rejections, particularly for the MAIL FROM domain, ensure that all necessary DNS records, including the A record, are correctly configured. This is a foundational step in email deliverability.
- Dedicated sending domains: When setting up dedicated sending domains, including A records for both MAIL FROM and Header From subdomains is a prudent step towards better reputation.
- Full DNS setup: An A record is just one part of a comprehensive DNS setup for email. It should be configured alongside SPF, DKIM, and DMARC records to ensure full authentication and optimal deliverability. You can learn more about verifying sending domains.
- Impact on reputation: A complete and correct DNS setup, including A records, contributes positively to domain reputation. Conversely, missing or incorrect records can negatively impact your sender score, potentially leading to emails landing in spam folders.
Marketer view
Email marketer from Email Geeks states that an A record is essential if referring to the MAIL FROM domain, but less critical though still recommended for the Header From domain. They note that any domain without an A record can appear quite suspicious to receiving servers.
Marketer view
Email marketer from Email Geeks explains that having an A record for the subdomain used in the RFC 5322 From header is a standard best practice, often seen with large ESPs. This record usually points to the client's website IP address, typically at the root domain level.
What the experts say
Email deliverability experts generally agree on the critical role of A records for the MAIL FROM domain, emphasizing that its absence can lead to immediate rejections. For the Header From domain, while not strictly an RFC requirement for mail flow, an A record is considered a strong best practice. Its presence contributes to domain legitimacy and transparency, acting as a positive signal to receiving systems. Experts advocate for a consistent and verifiable web presence linked to the sending domain's A record.
Key opinions
- Core DNS requirement: Experts affirm that A records are fundamental for any domain to resolve to an IP address. Without it, the basic internet lookup mechanisms fail, impacting any service associated with that domain, including email.
- Mail from domain validation: It is widely accepted that the domain in the MAIL FROM (envelope sender) address must have a valid A record. Receiving servers perform checks to ensure this, and failure can result in permanent rejections. This helps prevent spam and spoofing.
- Header from as a best practice: While RFCs may not strictly mandate an A record for the Header From domain for email delivery, experts consider it a crucial best practice for reputation. It adds a layer of transparency and trustworthiness to the sender.
- Signals legitimacy: A properly configured A record, especially one pointing to a live website or landing page, signals to ISPs and recipients that the sending domain is legitimate and actively managed, enhancing domain reputation and reducing spam classifications.
- Avoiding blocklists: Domains lacking expected DNS records, including A records, are more susceptible to being flagged by spam filters and potentially ending up on real-time blocklists or blacklists, impacting deliverability. For more information, see our guide on how your email address ends up on a blacklist.
Key considerations
- Dedicated IP vs. Shared: When using a dedicated IP, the A record for the sending domain should ideally point to that specific IP. For shared IPs, ensure your ESP manages this configuration effectively to maintain proper domain resolution.
- Subdomain strategy: If using different subdomains for various email streams (e.g., transactional vs. marketing), ensure each relevant subdomain has its own A record. This is similar to how SPF records are managed for subdomains.
- MX record dependency: Even if your sending domain doesn't need to receive email directly, if it has an MX record (which is usually for receiving), that MX record must point to a valid A or AAAA record. This forms a chain of trust within DNS.
- Aligning with reverse DNS: The IP address that the A record points to should ideally have a matching PTR record (reverse DNS) that resolves back to the sending domain. This alignment is a strong deliverability signal and often checked by receiving servers. Learn more about why reverse DNS is important.
Expert view
Deliverability expert from SpamResource emphasizes that the absence of fundamental DNS records, such as an A record for the MAIL FROM domain, is a strong indicator of an illegitimate sender and will likely result in immediate rejection by receiving mail servers.
Expert view
Deliverability expert from Word to the Wise advises that while the RFCs don't explicitly require a Header From domain to resolve, in practice, having a valid A record contributes to a positive domain reputation and improved deliverability, as it presents a complete and verifiable identity.
What the documentation says
Official documentation and RFCs highlight the foundational role of A records in DNS resolution, which indirectly but significantly impacts email deliverability. While RFCs focus on the technical mechanisms of email, they imply the necessity of proper DNS resolution for any domain referenced in an email. This includes the MAIL FROM domain for successful SMTP transactions and, by extension, the Header From domain for broader ecosystem trust and authentication mechanisms.
Key findings
- DNS foundation: A records are a fundamental DNS record type, mapping domain names to IPv4 addresses. This mapping is essential for any internet service, including email, to locate servers by their domain name. According to MailerSend, A records are necessary for DNS functionality.
- MX record dependency: While MX records specify mail servers, they must point to an A or AAAA record to function correctly. This means that even for domains that only send email but might have an MX record for bounce handling, the underlying A record is still crucial for resolution. AWS Repost discussions confirm this dependency.
- Domain resolution for email: DNS Made Easy documentation states that an A record is a fundamental requirement for DNS servers to function correctly. Without it, a domain would fail to resolve properly, directly affecting email delivery since mail servers wouldn't know where to connect.
- Authentication standards: Modern email authentication standards like SPF, DKIM, and DMARC rely heavily on accurate DNS records, including A records for proper domain resolution. Pressable's knowledge base indicates that these records are required for domains used to send email.
Key considerations
- RFC 5321 (MAIL FROM): The domain in the MAIL FROM command (also known as the envelope sender or bounce address) must be resolvable via DNS. While the RFC does not explicitly state an A record is mandatory, practical implementation by MTAs requires it for successful SMTP transactions.
- RFC 5322 (Header From): The Header From address (the one visible to recipients) is primarily for human readability and authentication alignment. While not directly involved in mail routing via A records, its resolution is a strong deliverability signal and often checked by spam filters for legitimacy. RFC 5322 specifies the format.
- Consistency with other records: A records must align with other DNS records like SPF, DKIM, and DMARC for proper email authentication. Misconfigurations, such as a missing A record for the domain specified in SPF, can lead to authentication failures.
- Impact on error messages: The absence of an A record for a sending domain can result in common error messages like "450 4.1.8 Sender address rejected: Domain not found," directly indicating a DNS resolution issue. Resolving these requires configuring the correct DNS records.
Technical article
Documentation from MailerSend outlines that A and AAAA records are foundational and essential for DNS. While other records are also important, these specific address records are critical for domains to resolve correctly on the internet.
Technical article
Documentation from DNS Made Easy states that an A record is a fundamental requirement for DNS servers to function properly. Without an A record, a domain would fail to resolve, preventing accurate IP address lookup for services like email.
Related resources
5 resources
Related pages
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Are A records needed for return-path domains?
What are PTR records and are they essential?
Is it bad to send email without an MX record?
Best practices for choosing an email sending domain
A simple guide to DMARC, SPF, and DKIM
Why your emails go to spam and how to fix it
Is email deliverable with an A record but no MX?
