What are the absolutely necessary DNS records for sending emails from a subdomain?

For email sending, the essential DNS records for a subdomain are MX, SPF (TXT), DKIM (TXT), and DMARC (TXT). These records are vital for authenticating your emails and ensuring they reach the inbox. A records are not directly required for email sending itself, but may be used for web presence or redirection.

Is an A record needed for email sending subdomains?

No, A records are not strictly required for email sending domains. Their primary role is to map a domain or subdomain to an IP address for web traffic. Your email service provider's infrastructure handles the actual email routing and sending.

Are SSL certificates required for email sending subdomains?

SSL certificates are generally not required for the act of sending emails. Email transmission uses TLS encryption server-to-server. However, if your email links (e.g., tracking links) point to a subdomain that you want to resolve securely over HTTPS, then an SSL certificate for that specific subdomain would be necessary.

Why is it important to use a subdomain for email sending?

Using a dedicated subdomain for email sending helps separate your email reputation from your main domain's reputation. This means if your email sending experiences issues (like hitting a blocklist), it is less likely to affect your main website's reputation or other services running on your primary domain.

How do I set up these DNS records for my subdomain?

Your ESP will provide the specific values for your SPF, DKIM, and DMARC records. You will then need to log into your domain's DNS management interface (usually with your domain registrar or DNS host) and add these records. It's crucial to ensure they are entered exactly as provided.

What DNS records are needed for email sending subdomains and are A records or SSL certificates required? - Technical - Email deliverability - Knowledge base

When setting up email sending, especially for marketing or transactional purposes, using subdomains is a common and recommended practice. It helps segment your email traffic and protects your main domain's reputation. A frequent question that comes up is what specific DNS records are needed for these subdomains, and whether A records or SSL certificates play a role in this setup.

The world of DNS records can feel a bit like navigating a maze, with various types of records serving different purposes. Understanding which ones are crucial for email deliverability versus those that serve other web-related functions is key to ensuring your emails land in the inbox and not in the spam folder. Let's break down the essential components for your email sending subdomains.

Essential DNS records for email sending

For email sending subdomains, the most critical DNS records are those that enable authentication and mail routing. These records tell recipient mail servers that your emails are legitimate and haven't been tampered with. Without them, your messages are highly likely to be flagged as spam or rejected outright.

Specifically, you'll need MX, SPF, DKIM, and DMARC records. These form the backbone of modern email authentication. Each plays a distinct role in verifying your sending domain and ensuring email deliverability. They help prevent phishing and spoofing, which are major concerns for mailbox providers.

MX records, or Mail Exchanger records, specify the mail servers responsible for receiving email for your subdomain. While your sending subdomain might not receive replies, some mail servers check for an MX record to ensure the domain is configured for email, even if it points to a null MX record. For more details on this, you can review information about DNS records for email.

SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) are essential for authenticating your sending domain. SPF records, which are TXT records, list the authorized IP addresses or mail servers that can send email on behalf of your subdomain. DKIM adds a digital signature to your outgoing emails, allowing recipient servers to verify that the email hasn't been altered in transit and that it genuinely originated from your domain. Both are critical for preventing spoofing and improving your sender reputation.

Record Type	Purpose	Example Value
MX Record	Directs incoming email for the subdomain (often set to a null MX for sending-only subdomains).	10 .
SPF (TXT) Record	Authorizes specific servers to send email on your subdomain's behalf.	v=spf1 include:_spf.example.com ~all
DKIM (TXT) Record	Adds a digital signature to outbound emails for verification.	v=DKIM1; k=rsa; p=MIGfMA0GC...
DMARC (TXT) Record	Specifies policies for handling emails that fail SPF or DKIM authentication.	v=DMARC1; p=none; rua=mailto:dmarc@example.com

The role of A records

A common point of confusion is whether A records are needed for email sending subdomains. An A record (Address Record) maps a domain or subdomain to an IPv4 address. While crucial for websites and web applications, A records are generally not a direct requirement for sending emails.

Your email service provider (ESP) or mail server handles the actual sending of emails, and it's their IP addresses that need to be authorized in your SPF record, not necessarily an A record pointing from your sending subdomain. You do not have to have an A record to send emails.

However, an A record might be set up for a sending subdomain if you want that subdomain to resolve to a web page, perhaps for brand consistency, or if you use a return-path domain that points to a specific IP for bounce processing. In these cases, the A record facilitates web traffic, not email sending directly. It's often considered good practice for your subdomain to resolve somewhere, even if just to a redirect to your main website. This can provide some transparency to recipients or curious parties who might look up your sending domain.

A records for email sending

Direct necessity: Not directly required for the act of sending emails.
Primary function: Maps a domain/subdomain to an IP address for web traffic.
Use cases: Used if the sending subdomain also hosts a web page or redirects, or for reverse DNS lookup consistency.
Impact on deliverability: Minimal direct impact on whether emails are delivered, but can enhance overall domain legitimacy if configured for a web presence.

CNAME records for email sending

Direct necessity: Often required by ESPs for white-labeling tracking and bounce domains.
Primary function: Maps a subdomain to another domain name (canonical name).
Use cases: Used for tracking clicks, open rates, and handling bounces via your ESP's infrastructure.
Impact on deliverability: Important for aligning your sending domain with tracking links and improving brand trust.

SSL certificates and email subdomains

Another common question is the necessity of SSL certificates for email sending subdomains. In most cases, you do not need an SSL certificate specifically for sending emails. SSL/TLS certificates primarily secure web traffic (HTTPS) and encrypt data between a web server and a browser.

Email transmission uses a different protocol (SMTP, POP3, IMAP), which also supports encryption, but this is handled by Transport Layer Security (TLS) during the mail transfer itself. This TLS encryption happens server-to-server and doesn't require an SSL certificate on your sending subdomain's DNS records.

Where SSL certificates become relevant is for any web assets or tracking domains associated with your email sending. For example, if your email contains links that point to a tracking subdomain (e.g., clicks.yourdomain.com) and you want those links to load securely over HTTPS, then you would need an SSL certificate for that specific subdomain. This is good for user trust and avoids browser warnings.

Beware of unnecessary SSL purchases

Some third-party providers or IT departments might suggest purchasing expensive wildcard SSL certificates for your email sending domains. However, for the sole purpose of email sending, this is usually unnecessary and adds significant overhead. If you need SSL for associated web properties, consider using free options like Let's Encrypt, which provides free, automated certificates.

Setting up your email subdomains

Setting up your email sending subdomains correctly is crucial for maximizing your email deliverability and maintaining a strong sender reputation. It involves more than just picking a subdomain; it requires careful configuration of specific DNS records.

Always consult your email service provider's documentation for the exact DNS records they require. They will provide specific values for your SPF, DKIM, and DMARC records tailored to their sending infrastructure. These are often TXT records, and for DKIM, they typically include a unique selector.

Beyond the initial setup, continuous monitoring of your email deliverability and DNS records is important. Tools can help you check your DNS configuration and identify any issues that might affect your sender reputation or lead to your emails being placed on a blocklist (or blacklist).

Example DNS records for a sending subdomain (send.example.com)DNS

Host: mail.example.com
Type: MX
Value: 10 mailserver.example.net

Host: send.example.com
Type: TXT
Value: "v=spf1 include:spf.mailservice.com ~all"

Host: s1._domainkey.send.example.com
Type: TXT
Value: "v=DKIM1; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA..."

Host: _dmarc.send.example.com
Type: TXT
Value: "v=DMARC1; p=none; rua=mailto:dmarc-reports@example.com"

Remember, the primary goal is to establish trust with mailbox providers. Correctly configured DNS records for email authentication are fundamental to achieving this trust and ensuring your emails reach their intended recipients. Understanding different types of DNS records is important.

Views from the trenches

Best practices

Always use a dedicated subdomain for email sending to isolate reputation.

Carefully follow your email service provider's instructions for DNS setup.

Implement SPF, DKIM, and DMARC for all sending subdomains.

Ensure your SPF record authorizes all servers sending email on your behalf.

Common pitfalls

Forgetting to add required DKIM and DMARC records for the subdomain.

Incorrectly configuring SPF records, leading to failed authentication checks.

Assuming A records or SSL certificates are required for email sending itself.

Not removing old, unauthorized IPs from your SPF record, creating security gaps.

Expert tips

Consider setting up a simple web page or redirect on your sending subdomain's A record for brand presence and transparency.

For tracking links in emails, secure them with an SSL certificate to ensure they load over HTTPS.

Automate the renewal of any SSL certificates for tracking domains using services like Let's Encrypt.

Regularly audit your DNS records to ensure they are current and correctly configured.

Marketer view

Marketer from Email Geeks says: We want to split and update our sender email addresses, and our IT department is asking about A records. What records are truly necessary for Mailchimp?

2019-12-11 - Email Geeks

Expert view

Expert from Email Geeks says: The A records are not the primary concern here; for sending emails from a subdomain, you need to focus much more on the TXT records for SPF, MX, DKIM, and DMARC. You don't necessarily have to have an A record to send emails, but you must have proper SPF, MX, and DKIM configured.

2019-12-11 - Email Geeks

Key takeaways for your email setup

In summary, while A records and SSL certificates serve important functions for web properties, they are generally not strict requirements for the core process of sending emails from subdomains. The most crucial DNS records for email sending are MX, SPF, DKIM, and DMARC.

Focus your efforts on correctly configuring these authentication records as per your email service provider's guidelines. This foundational setup will significantly impact your email deliverability and help maintain a healthy sender reputation, ensuring your messages reach their intended recipients without unnecessary blocklisting (or blacklisting) or spam folder placement.