Definition
rDNS is the inverse of standard DNS — instead of looking up an IP for a domain, it looks up the domain for an IP. When your sending server connects to a receiving server, the ISP checks that the IP's rDNS matches the domain in your HELO/EHLO greeting. A mismatched or missing rDNS record is a strong spam signal. Setting up rDNS requires your hosting provider to add a PTR record pointing your sending IPs to your sending domain. Most ESPs handle this automatically, but custom SMTP setups require manual configuration.
Related Glossary Terms
AOL Mail for Email Marketers
AOL Mail is a legacy email provider with specific deliverability requirements and rendering quirks, now operating as part of the Yahoo+AOL network under shared infrastructure.
BIMI
BIMI (Brand Indicators for Message Identification) is an email standard that allows brands to display their logo next to their emails in supported email clients. It requires DMARC enforcement at quarantine or reject policy.
Bounce Rate Threshold
A bounce rate threshold is the percentage of hard or soft bounces at which email platforms and ISPs begin to penalise sender reputation, typically around 2-5%.
Bounce Rate
Email bounce rate is the percentage of emails that were rejected by the receiving server before reaching the recipient. It is a key indicator of list health and data quality.
Bulk Email Marketing
Bulk email marketing is the practice of sending a single email campaign to a large list of subscribers simultaneously, typically for promotional, newsletter, or announcement purposes.
Email Deliverability
Email deliverability is the ability to land in the recipient's inbox rather than the spam folder. It depends on sender reputation, authentication, list quality, and content practices.