How does missing or different reverse DNS (rDNS) impact email deliverability, and when is a dedicated IP address needed?

The consensus is that reverse DNS (rDNS) significantly impacts email deliverability, with most sources emphasizing the importance of a correct rDNS record for authentication and sender reputation. A missing or incorrect rDNS can lead to emails being flagged as spam, rejected by ISPs, or negatively impacting inbox placement, especially with enterprise filters. Different rDNS across a range isn't necessarily a problem if those IPs aren't actively sending. Regarding dedicated IPs, the need arises when senders require more control over their reputation, send a high volume (generally above 5,000 emails/day or 50,000/month), or seek isolation from other senders. However, success with a dedicated IP hinges on maintaining a clean email list and consistent sending practices. Some suggest that if you can't maintain a good sender score, a shared IP with a reputable ESP might be preferable. The decision depends on individual circumstances and priorities, and not assuming all IPs in a range are used for sending mail. A minority opinion suggests rDNS is less critical if the IP doesn't point nowhere, but this is outweighed by the majority view emphasizing its importance.

The impact of missing or incorrect reverse DNS (rDNS) on email deliverability varies, with some experts considering it crucial for sender reputation and others downplaying its importance if the IP doesn't point nowhere. Correct rDNS records help ISPs verify the legitimacy of emails, improving deliverability and open rates. A dedicated IP address is needed when senders require more control over their reputation, send high volumes (50,000+ per month), or want to isolate their sending from others. However, maintaining a clean email list and consistent sending practices are essential for a dedicated IP's success; otherwise, a shared IP with a reputable ESP may be better.

Experts agree that reverse DNS (rDNS) plays a significant role in email deliverability. Missing or incorrect rDNS records can negatively impact delivery, especially for enterprise filters and may cause emails to be rejected or sent to spam. While some may downplay rDNS importance for IP ranges not actively sending mail, a correct rDNS record is generally seen as a crucial part of email authentication. A dedicated IP address is recommended when senders need more control over their reputation and sending volume.

Official documentation consistently highlights the importance of reverse DNS (rDNS) for email deliverability. Missing or incorrect rDNS records can lead to emails being flagged as spam or rejected outright, as many servers use rDNS for identity verification. Google recommends a dedicated IP for senders exceeding 5,000 emails per day, emphasizing the need for reputation management at that volume. Proper rDNS configuration is deemed a basic requirement for authentication by Postfix.