How do I set up or change a PTR record for my email sending IP?

PTR records are usually managed by your internet service provider (ISP) or hosting provider, as they own the IP address range from which you send emails. You need to contact them to request the creation or modification of your PTR record to point to your mail server's hostname.

Is a PTR record absolutely essential for email deliverability?

While not strictly required by all standards, many mail servers perform reverse DNS lookups and will flag or reject emails from IPs without a valid PTR record. It is highly recommended to have one for good email deliverability and to avoid being marked as spam.

What is Forward-Confirmed reverse DNS (FCrDNS) and why does it matter?

FCrDNS (Forward-Confirmed reverse DNS) is when an IP address's PTR record resolves to a hostname, and that hostname's A record resolves back to the original IP. This perfect match enhances trust and improves email deliverability, as it helps mail servers verify the authenticity of the sender.

What happens if my domain is missing an MX record?

An MX record tells other mail servers where to send incoming emails for your domain. Without an MX record, other mail servers won't know which server is responsible for your domain's email, causing incoming emails to bounce and be undeliverable. It is critical for receiving email.

How do PTR, A, and MX records relate to SPF, DKIM, and DMARC?

These records are foundational for email authentication. SPF records often use A and MX lookups, while DKIM relies on A records for domain resolution. DMARC policies then use the results of SPF and DKIM authentication. Proper configuration of PTR, A, and MX records helps ensure these authentication methods pass correctly.

What are PTR records and are they essential for email deliverability, along with other DNS records like A and MX? - Technical - Email deliverability - Knowledge base

When you send an email, it’s not just about hitting “send” and hoping for the best. Behind the scenes, a complex system of checks and balances ensures your message travels from your server to the recipient’s inbox. At the heart of this system are DNS records. These records act like the internet’s phonebook, translating human-readable domain names into machine-readable IP addresses, and vice-versa.

Specifically for email, three types of DNS records are absolutely foundational: PTR, A, and MX records. Understanding their roles isn't just for IT professionals or network administrators, it’s crucial for anyone who relies on email for business or communication, because they significantly impact whether your emails actually reach their destination or end up in a spam folder.

Many email providers, like Google and Yahoo, heavily rely on these records to authenticate senders and filter out malicious or unsolicited mail. Let's dive into what each of these records does and why they're so essential for maintaining good email deliverability.

What are PTR records and how do they work?

When we talk about PTR records, we're discussing reverse DNS. Unlike a typical DNS lookup where you type a domain name and get an IP address, a PTR record does the opposite: it maps an IP address back to a domain name. This reverse lookup is a critical security measure in the email world.

Many mail servers perform a reverse DNS lookup on the IP address of the incoming mail server. If the IP address does not have a valid PTR record, or if the PTR record doesn't match the domain that claims to be sending the email, it raises a red flag. This inconsistency can lead to your emails being flagged as spam or outright rejected by the receiving server.

The ideal scenario is called Forward-Confirmed reverse DNS (FCrDNS), which means both the forward (A record) and reverse (PTR record) lookups match perfectly. For instance, if mail.example.com resolves to 192.0.2.1, then 192.0.2.1 should resolve back to mail.example.com. This consistency builds trust with receiving mail servers.

Example PTR Record

1.1.1.1.in-addr.arpa. IN PTR mail.example.com.

A and MX records in email infrastructure

While PTR records handle the reverse lookup, A and MX records manage the forward direction of DNS. An A record (Address Record) maps a domain name to its IPv4 address. For example, when you type www.suped.com into your browser, an A record tells your computer which IP address to connect to. For email, the A record typically points to the IP address of your mail server.

MX (Mail Exchanger) records are specifically for email routing. They tell other mail servers where to send emails for your domain. Without a correctly configured MX record, incoming emails to your domain would have no direction and would bounce back to the sender. This is why MX records are considered absolutely critical for any domain that expects to receive email.

While MX records are paramount for receiving email, their proper configuration also indirectly impacts your sending reputation. A well-configured and accessible MX record demonstrates that your domain is legitimate and professionally managed, which can positively influence how other mail servers perceive your outgoing mail. This forms part of the overall trust signals that contribute to good email deliverability.

A record

Purpose: Maps a domain name (like mail.example.com) to an IPv4 address.
Function for email: Allows other servers to find the IP of your mail server for sending and receiving. It’s part of the forward DNS lookup.
Impact on deliverability: Essential for mail servers to connect. Missing or incorrect A records can prevent mail flow entirely.

PTR Record

Purpose: Maps an IP address back to a domain name (reverse DNS).
Function for email: Used by receiving mail servers to verify the identity of the sending server. This is a critical anti-spam check.
Impact on deliverability: Lack of a matching PTR record is a common reason emails get blocked or sent to spam. It directly impacts sender reputation and trust.

Why these DNS records are crucial for deliverability

The collective proper configuration of PTR, A, and MX records is fundamental for robust email deliverability. When these records are missing or misconfigured, it signals to receiving mail servers that your domain might not be trustworthy. This can significantly hurt your sender reputation, making it much harder for your legitimate emails to reach the inbox.

For instance, without a matching PTR record, many mail servers will automatically view your sending IP as suspicious. This is a common tactic used by spammers, so mail servers are often configured to be wary of senders that lack proper reverse DNS. You might find your emails ending up in the spam folder or being rejected outright, leading to increased bounce rates.

Similarly, incorrect A or MX records can cause delivery failures. If your A record doesn't point to the correct mail server IP, or if your MX record is malformed, other servers simply won't know where to send mail for your domain. This can lead to significant deliverability issues and can even land your sending IP or domain on a blocklist (or blacklist), which you can check with a blocklist checker. Maintaining these records is a foundational step in ensuring your emails are trusted and delivered.

DNS Record	Primary Function	Impact on Email Deliverability
PTR (Pointer) Record	Maps an IP address back to a hostname (reverse DNS lookup).	Essential for server authentication and anti-spam. Without it, emails are often rejected or marked as spam.
A (Address) Record	Maps a hostname to an IPv4 address.	Allows mail servers to find your sending server's IP. Mismatched A and PTR records (not FCrDNS) can trigger spam filters.
MX (Mail Exchanger) Record	Specifies the mail servers responsible for receiving emails for a domain.	Crucial for receiving emails. Its presence and correct configuration signal a legitimate domain, influencing sender reputation.

Configuring your DNS for optimal email performance

Configuring your DNS records correctly is not just a technicality, it's a fundamental part of a robust email strategy. For PTR records, you typically won't manage these directly in your domain's DNS settings. Instead, they are managed by the entity that owns the IP address range from which you send emails, usually your hosting provider or internet service provider (ISP).

You'll need to contact them to request the creation or modification of your PTR record. Make sure the PTR record resolves to the same hostname that your sending server identifies itself as during the HELO/EHLO handshake. This matching is critical for establishing trust.

For A and MX records, you'll manage these within your domain's DNS control panel. Ensure that your A record points to the correct IP address of your mail server and that your MX records specify the correct mail servers with appropriate priority values. A common best practice is to have multiple MX records with different priorities for redundancy. You can learn more about general DNS record types on the Cloudflare website.

Regularly reviewing and updating these DNS records is vital, especially if you change hosting providers, switch email service providers, or modify your network infrastructure. These records are the foundation upon which more advanced email authentication protocols like SPF, DKIM, and DMARC are built, and their accuracy is paramount for maintaining excellent email deliverability.

Best practices for DNS configuration

Ensure FCrDNS: Your IP's PTR record should resolve to a hostname, and that hostname's A record should resolve back to the same IP. This full cycle builds trust.
Proper MX records: Always have MX records for your domain, even if your sending infrastructure handles bounces differently. It signals legitimacy.
Subdomain management: Use dedicated subdomains for email sending, especially for marketing or transactional emails. This isolates your main domain's reputation.
Regular checks: Periodically verify your DNS records using online tools to ensure they are correctly propagated and consistent.

Views from the trenches

Best practices

Always ensure your sending IP has a PTR record that matches your mail server's hostname for strong authentication.

Set up correct MX records for your return-path domain to handle bounces effectively and signal domain legitimacy.

Verify FCrDNS (Forward-Confirmed reverse DNS) where both A and PTR records align to enhance sender trust.

Utilize dedicated subdomains for email sending to protect your main domain's reputation from sending issues.

Regularly monitor your DNS settings for consistency, as misconfigurations can lead to deliverability problems.

Common pitfalls

Forgetting to set up a PTR record, causing emails to be blocked or filtered as spam by many receiving servers.

Having an MX record that points to a non-existent or misconfigured mail server, leading to email bounces.

Assuming A records for return-path domains are always necessary; many legitimate return paths function without them.

Not aligning your HELO/EHLO hostname with your PTR record, which can result in trust issues with email receivers.

Neglecting to update DNS records after changing IP addresses or mail server configurations.

Expert tips

For optimal deliverability, ensure your sending IPs have PTR records. While FCrDNS is ideal, it’s not universally adopted for all return-path domains, so focus on the PTR for your sending IP.

An MX record for your return-path domain is much more critical than an A record. Some systems might flag your emails if this isn't present.

While an A record on a return-path domain isn't strictly necessary for deliverability by most ISPs, having it as a fallback or for consistency can be beneficial.

Many email service providers (ESPs) handle their DNS setups for return-path domains. They may or may not include A records, but they will prioritize correct MX and PTR.

The email system often relies on subtle signals like DNS configuration to judge sender legitimacy. Even minor misalignments can contribute to negative reputation.

Marketer view

Marketer from Email Geeks says a PTR record is used for reverse DNS entries, which helps look up the hostname associated with an IP address.

2019-11-07 - Email Geeks

Marketer view

Marketer from Email Geeks says when forward (A record) and reverse (PTR record) lookups match, it's called Forward-Confirmed reverse DNS (FCrDNS), which is important for sender verification.

2019-11-07 - Email Geeks

Ensuring your emails land in the inbox

PTR, A, and MX records are more than just technical details. They are foundational elements that directly influence your email deliverability and sender reputation. While each record serves a distinct purpose, their combined proper configuration forms a strong signal of legitimacy to receiving mail servers, helping your emails bypass spam filters and reach their intended recipients.

For PTR records, remember that they enable reverse lookups, which are a key anti-spam mechanism. Ensuring your sending IP has a matching PTR record that aligns with your mail server's hostname is crucial. For A records, they ensure your domain name correctly points to your mail server’s IP, facilitating forward DNS resolution.

Finally, MX records are indispensable for receiving emails, guiding incoming mail to the correct server. Neglecting any of these can lead to delivery failures, classification as spam, or even placement on a blocklist (or blacklist). Proactive management and regular checks of your DNS records are vital steps in building and maintaining a trustworthy email sending infrastructure.