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What is the best practice for reverse DNS resolution when sending email via an ESP?

Summary

When sending emails through an Email Service Provider (ESP), understanding reverse DNS (rDNS) resolution is crucial for maintaining strong sender reputation and ensuring optimal deliverability. Unlike self-hosted mail servers where you typically manage your own rDNS, ESPs often control these records for their shared or dedicated IP addresses.

What email marketers say

Email marketers often encounter questions about reverse DNS resolution, especially when operating through an Email Service Provider (ESP). There's a common desire for the reverse DNS to explicitly point to their specific sending domain, even if they are on a shared IP infrastructure. However, the reality of ESP operations often dictates otherwise.

Marketer view

A marketer from Email Geeks observes that an IP address, when queried for reverse DNS, resolves directly to Sparkpost. This indicates that the Email Service Provider (ESP) is managing the reverse DNS records for its allocated IP space. This is a common setup for ESPs providing email sending services.

24 Apr 2019 - Email Geeks

Marketer view

A marketer from Email Geeks points out that they have seen numerous cases where Email Service Providers (ESPs) configure their reverse DNS (rDNS) to resolve to the sender’s domain rather than their own. This suggests that while it might not be the default, some ESPs offer this level of customization.

24 Apr 2019 - Email Geeks

What the experts say

Email deliverability experts highlight that the optimal reverse DNS (rDNS) setup for an Email Service Provider (ESP) depends largely on whether a client is using shared or dedicated IP addresses. For shared IPs, ESPs retain control over rDNS, a standard practice that rarely causes issues. However, dedicated IPs offer more flexibility for sender-specific rDNS configurations, which can further strengthen a sender's identity and deliverability.

Expert view

An expert from Email Geeks indicates that correctly looking up reverse DNS requires providing the specific IP address in question. This highlights the foundational step of identifying the IP for accurate diagnostic checks on reverse DNS configurations.

24 Apr 2019 - Email Geeks

Expert view

An ESP expert from Email Geeks confirms that their organization's reverse DNS (rDNS) resolves to their own domain, not the sending domains of their clients. This is a common operational model for Email Service Providers and is not a default cause for deliverability concern.

24 Apr 2019 - Email Geeks

What the documentation says

Official documentation and technical guides consistently emphasize the importance of reverse DNS (rDNS) as a fundamental component of email deliverability and anti-spam measures. They detail how PTR records link IP addresses to domain names, enabling recipient mail servers to verify the authenticity of the sending source. While the direct control over rDNS may vary with ESPs, the underlying principles of verification and consistency remain paramount for optimal email flow.

Technical article

Documentation from Mailgun explains that understanding reverse DNS (rDNS) is crucial for improving email deliverability. They provide detailed insights into what rDNS entails, why it holds significant importance for senders, common configuration mistakes to avoid, and how users can effectively set up their rDNS records with their service.

10 Aug 2023 - Mailgun

Technical article

Documentation from MailerSend clarifies that email servers utilize PTR records to perform a reverse DNS lookup. This process is essential for verifying that the domain name associated with an IP address matches the corresponding domain name, serving as a critical step in authenticating the email sender and preventing spoofing.

20 Feb 2024 - MailerSend

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