Where can I find a list of bounce/block codes and their explanations?

Email marketer from StackExchange explains that the 5xx range of codes generally indicates an issue with the recipient's address (doesn't exist, mailbox full, spam filter) while the 4xx codes generally indicates a temporary server issue.

Email marketer from ActiveCampaign answers by differentiating between hard bounces (permanent reasons like invalid addresses) and soft bounces (temporary issues like full inboxes), and explains their impact on email marketing strategies.

Email marketer from EmailAcademy provides a list of common email bounce codes and suggests best practices for managing bounces to maintain a healthy email list.

Email marketer from MailerQ answers that bounce codes are categorized into three digits and often include an enhanced code for more precision. The initial digit signifies the class of response, whether it's a temporary failure (4xx), permanent failure (5xx), or success (2xx).

Email marketer from Litmus answers by explaining the importance of monitoring bounce rates and proactively removing bounced email addresses from your mailing list to maintain a good sender reputation and improve deliverability.

Email marketer from GlockApps answers by suggesting using a bounce analyzer tool to automatically categorize and interpret bounce codes, helping identify and fix deliverability problems efficiently.

Email marketer from Postmark explains common bounce reasons, categorizing them and providing solutions. They highlight that understanding these codes helps improve email deliverability.

Email marketer from Reddit shares that some ESPs provide more user-friendly explanations than raw SMTP codes, recommending checking the specific documentation of your email service provider.

Email marketer from SendPulse answers that email bounce codes, also known as SMTP error codes, indicate why an email wasn't delivered; they are divided into 4xx (temporary errors) and 5xx (permanent errors).

Expert from Email Geeks shares a link to Pardot's blog post about bounce codes: <https://www.pardot.com/blog/bounce-codes/>.

Expert from SpamResource explains that enhanced status codes provide more detailed explanations than standard SMTP codes, structured as x.y.z, and that understanding these codes requires looking up their meanings in relevant documentation.

Expert from SpamResource explains that NDRs (Non-Delivery Reports) contain vital information about why an email bounced, including SMTP error codes and human-readable explanations, though these explanations may sometimes be vague.

Expert from Word to the Wise, Laura Atkins, explains bounce handling and feedback loops are important for maintaining deliverability and provides some general information on the topic.

Expert from Email Geeks responds that the IANA docs aren't useful, and that ISPs/Filters use codes of their own creation.

Documentation from ietf.org specifies the enhanced mail system status codes that provide standardized explanations for delivery failures in SMTP.

Documentation from AWS explains that Amazon SES sends bounce notifications containing information about why an email wasn't delivered, including bounce codes and descriptions, aiding in troubleshooting delivery issues.

Documentation from Mailjet provides a comprehensive list of SMTP error codes, explaining that 4xx codes are temporary errors that might resolve on their own, while 5xx codes indicate permanent failures requiring intervention.

Documentation from Oracle explains the email bounce codes and their categorization into hard bounces, soft bounces, and technical bounces. Hard bounces indicate permanent delivery failures, soft bounces indicate temporary issues, and technical bounces refer to problems like DNS errors or server timeouts.

Documentation from IONOS explains common email bounce codes, dividing them into 4xx (temporary failures) and 5xx (permanent failures), with examples like 421 (Service not available) and 550 (mailbox unavailable).