Smtp bounce codes. Aug 13, 2025 · Later, in a DSN (bounce message).
Smtp bounce codes Sep 12, 2024 · In this little guide, we will explain how to manage email bounce codes, and share a full list of email bounce codes and what they stand for. May 22, 2025 · Understanding SMTP bounce codes is crucial for email deliverability. What is an SMTP response code? An SMTP code is a standardized response sent by a mail server to indicate the status of an email. 1 bounce error, often seen with 'Recipient address rejected: Access denied', and discover best practices for troubleshooting and resolution to improve email deliverability. It's important to look at the SMTP Bounce codes to determine why a bounce occurred. However, an internet service provider (ISP) might return a hard bounce even if the email address is valid. They are three digit codes. However, they are all three digits long and do generally begin with a number that puts them into one of four categories: 4XX – Codes that start with 4 – These are referred to as soft bounce errors. This guide covers identifying root causes, understanding bounce messages, and implementing effective strategies to improve email deliverability and sender reputation. Gmail SMTP errors and codes You might see the error messages and codes on this page when send email to Gmail accounts. The codes are About SMTP bounce codes The information on this page describes the RFC standards, not the actual implementation on MTA/Mail Server side. Jun 23, 2025 · Learn how to parse SMTP responses to accurately identify hard and soft email bounces, understand SMTP codes (4xx and 5xx), and implement effective strategies for improving email deliverability and sender reputation. Use individual bounce responses in conjunction with the category recommendations below. There are many reasons why a sender will receive an NDR, but typically it is based on an SMTP rejection code, or it would be a timeout failure to deliver an email. Our SMTP Field Manual provides a directory of common bounce codes from popular mailbox providers and spam filters, along with actionable advice on how you should handle these bounce notifications. Instead, it is “bounced” back to you (or sometimes silently dropped) with a notification indicating a delivery failure. Jun 19, 2025 · Segment your audience for IP warming and gradually increase volume to specific domains like Microsoft to build reputation systematically. 4. Bounce messages usually contain an SMTP status code and some additional details explaining why delivery was unsuccessful. Jan 8, 2025 · Explore common email bounce codes, their meanings and how they help identify delivery issues to improve your email performance. Overview At its core, SMTP is a set of rules and conventions that define how email messages should be structured, transmitted, and received between mail servers. Typically, hard bounces are returned with an Simple Mail Transfer Protocol (SMTP) code in the 500 range. 4. This is the primary indicator of the delivery status, providing a general category for the List of SMTP server return codes This is a list of Simple Mail Transfer Protocol (SMTP) response status codes. What to do if you’re seeing high bounce rates What Are Email Bounce Codes? Bounce codes are status messages returned by receiving mail servers when they reject or delay delivery of an email. What are email bounce codes? Know everything about email bounce and error codes and how to fix it via this article. 0, instead of a 3-digit number, e. To learn more about bounce handling, see Bounce Mail Management in Email Studio and Bounces in Marketing Cloud. This comprehensive guide provides expert insights and answers to commonly asked questions, empowering you to optimize your email campaigns and ensure maximum deliverability. Diagnostic Troubleshooting: A system administrator reviews SMTP bounce codes reported in bounce messages MailChannels customers get automatic access to ResponseAnalytics, which decodes bounce messages and SMTP errors into human-readable explanations—so you don’t have to Google codes manually. Instead, it's a Mailgun-specific message disposition response offered up by their platform after the Mailgun platform has attempted to deliver the message for a period of time Feb 14, 2024 · By familiarizing themselves with common bounce types and error codes, senders can take appropriate actions to address underlying issues and improve email deliverability. Traditional Bounce Codes When you add the Email Invalid Cause to display as a Column to any of your Deliverability Smartlists, you will see a code value, and potentially a suffix as well, to help you understand the reason for the Bounce. X Bounce Codes (Enhanced SMTP bounce responses) which are composed of 3 numbers separated by decimal points i. See our guide to avoiding email spam. Admins can learn about SMTP errors and non-delivery reports (also known as NDRs or bounce messages) that are generated in Exchange Online. Traditional vs. , 421), while those starting with “5” denote a hard bounce (e. Compared to traditional three-digit bounce keys, marketers use enhanced bounce codes to pinpoint the exact cause of the delivery issue. May 26, 2013 · If you receive an email bounce, you can look in the bounce message to find the proper error code that will give you the reason for the bounce. 0 or 5. There is a pressing need for a rich machine-readable, human language independent status code for use in delivery status notifications [DSN May 27, 2025 · Some of the most common phishing bounce codes along with their reason for occurring and resolutions are shown below. There are two main types: Hard bounces (5xx codes): Permanent failure. SMTP is independent of the particular transmission subsystem and requires only a reliable ordered data stream channel. Fatal Bounces (500-series errors): Permanent failures where the email cannot be delivered and requires corrective action. First, there's the SMTP response code, a three-digit number defined by RFC 5321. 0. It also includes a glossary of common SMTP error codes along with their meanings and their fixes. SMTP Codes and Bounce Messages While the general rule is that Soft Bounces are temporary issues, and that Hard Bounces are permanent, the reality is that every mail server is configured differently and there are no hard rules; the power to decide whether an email message is received, and the reason given (if any) for a bounce belongs 100% to If incoming or outgoing messages are bouncing, check the bounce messages for an SMTP error code that can help you diagnose the problem. Apr 25, 2016 · Codes in the 400 range are generally Soft Bounces Codes in the 500 range are generally Hard Bounces The SMTP response codes below are common codes that a mail administrator may use. 400 – are a more dependable source for understanding why your emails bounce. Mail administrators and providers can also create unique SMTP response codes and details. It's important to look at the SMTP Bounce codes to determine why. Note that beside the numerical 3-digit value, the SMTP response contains itself a human readable part. These logs contain the specific SMTP (Simple Mail Transfer Protocol) reply codes and messages, which are crucial for understanding the exact reason for the bounce. The reason they are different is that bounce handling in Portrait Dialogue is done by a third-party library called BoogieBounce. May 1, 2025 · Bounce errors get brought up quite a bit but what about SMTP errors? SMTP, or Simple Mail Transfer Protocol, is the language servers use to talk to each other when sending emails. RFC 5321 SMTP October 2008 1. Mail server administrators can customize the messages that accompany codes, so messages can be different from server to server. , 550). This is often a temporary issue, and once the recipient clears space or the mailbox size is increased, emails can be delivered. Sep 7, 2023 · A glossary of email bounce codes to help you understand why your emails weren't delivered. While this document specifically discusses transport over TCP, other transports are possible Apr 27, 2025 · Understand what soft bounces are, their common causes like full inboxes or server issues, and effective strategies to fix them. It must be verified with Amazon SES. Each bounce code corresponds to a specific type of email delivery issue, helping you identify the underlying problem. catch -all - These emails are impossible to validate without sending a real email and waiting for a bounce. 1, 4. traditional SMTP bounce codes Los códigos de rebote SMTP tradicionales son números de tres dígitos (por ejemplo, 554) que indican si un correo electrónico se ha entregado correctamente o no. SenderScore's email bounce error guide to help you troubleshoot and fix email error code 5. It establishes a reliable and effic Aug 30, 2024 · Conclusion on email bounce codes Making sense of email bounce codes is a big win for any email marketer. These advanced keys make it easier for Bounces, bounce, hard bounce, soft bounce, soft, hard, transfail, transient Simple Mail Transfer Protocols (SMTP) are codes sent to you from various mail servers, showing the reasons emails you sent were rejected. Jul 6, 2025 · Learn how to troubleshoot and resolve common 554 SMTP soft bounces in Salesforce Marketing Cloud. 5. Status codes are issued by a server in response to a client's request made to the server. Oct 27, 2025 · Emails bouncing back with confusing SMTP errors? Learn what codes like 550, 421, and 554 actually mean, what causes them, and how to fix bounceback issues to improve deliverability. This guide explains different bounce types, their impact on your sender reputation, and how to effectively manage them to avoid email blocklists and ensure successful email campaigns. Feb 22, 2016 · I'd like to ask real mailserver administrators from here about some smtp error codes - I take care of some customer's mailing systems, and there is a wide range of May 18, 2023 · What is SMTP Error 554? SMTP Error 554, also known as a permanent error, is an error code returned by the receiving server to the sending server when an email cannot be delivered. This can Jun 13, 2025 · Learn what email bounce is and discover 15 powerful ways to fix, prevent, and reduce bounce rate for better deliverability and inbox placement. The email will never be delivered. It's not the raw, unadulterated SMTP response directly from the recipient's mail server. SMTP Error Codes An SMTP error, or Delivery Status Notification (DSN), indicates that an email could not be delivered, either due to a temporary or permanent problem. What is Enhanced bounce codes? These are another type of SMTP status codes. Learn how to diagnose these temporary delivery failures and improve your email deliverability. The events in this report relate to all subscribers for a particular send. SMTP Error 451 Explained If your email bounce report mentions the error code: The enhanced SMTP status codes giving more specific information in addition to the basic reply codes. Jun 21, 2025 · The message "Hard bounce - User Unknown [5. Oct 30, 2024 · Understanding SMTP bounce codes, their meanings, and how they impact email delivery. Learn how to interpret SMTP errors, differentiate between hard and soft bounces, and use this data to improve your email deliverability and sender reputation. Aug 12, 2025 · A Non-Delivery Report or Bounce Message is a report generated by the mail server to inform the sender that the email delivery was not successful. In these cases, Oracle Eloqua converts the hard bounce to a soft bounce. You may find both in the bounce reasons for a particular email campaign. When something breaks during that conversation, the server returns a code to explain what happened. Understand email error codes and bounce messages. You get a non-delivery email with Enhanced Status Codes like 5. 5xx codes (permanent failures / hard bounces): These codes signify a permanent error, and the server will not attempt to resend the message. Leverage SFMC's tracking data and SMTP bounce codes to identify specific reasons for non-delivery or high spam placement. , 554) that indicate whether an email was delivered successfully or not. Aug 9, 2021 · Decode email bounce codes and understand the difference between soft bounce and hard bounce with our comprehensive lookup and definitions. SMTP error messages follow this format. (504). These response codes are the only ways in which email servers communicate over a network. They help identify the reasons your emails bounced and are sometimes demanded by your email validation service providers to understand what causes your bounces. Jan 20, 2025 · Bounce Classification Codes and Definitions This guide outlines the potential errors you may encounter when sending messages through our service. Jun 2, 2025 · Learn how to troubleshoot email bounce messages, interpret SMTP error codes, and apply practical solutions to improve your email deliverability. 2, etc. 0) and the traditional SMTP Status Codes which have 3-digit codes without decimal points i. invalid - These are emails that we determined to be invalid, please delete them from your mailing list. 1. Codes starting with “4” usually indicate a soft bounce (e. Learn to manage hard and soft bounces for improved deliverability. Jan 8, 2025 · This guide teaches you how to read SMTP error codes. Unless otherwise stated, all status codes described here is part of the current SMTP standard, RFC 5321. Now, doesn’t that sound like a plan? Navigating soft bounces caused by transient issues or addressing hard If you run a Bounce Event Extract File, there’s an SMTP Code column that lists a code related to each bounce. Nov 7, 2025 · Email bounce backs occur when an email is sent to an Email Security. Apr 23, 2024 · The result of this is a list of possible SMTP status codes that you will often see included in bounce messages when analyzing your returns. SMTP Reply Code— The SMTP reply code, as defined by RFC 5321. Apr 29, 2020 · SMTP response codes are the primary source for debugging issues related to bounce. Email bounce codes can be tricky to decipher, but following a few best practices can help avoid and reduce your bounce rates. Z format (details below). In most cases, the mailbox providers return two pieces of information in the event of a bounce, a traditional SMTP response status code and an enhanced mail system status code. 1 Jan 23, 2025 · Here, we explain exactly what these response codes are and the main ones you need to know. These responses communicate whether the message has been accepted, temporarily delayed, or permanently rejected. May 19, 2020 · This video installment covers how to use Simple Mail Transfer Protocol codes provided by MBPs to better understand email performance and how to fix any issues. Bounce Classification Codes Following is a list of bounce classification codes and their meanings Classification Name Description Category 1 Undetermined The response text could not be identified Undetermined 10 Invalid Recipient The recipient is invalid Hard 20 Soft Bounce The message soft bounced Soft 21 DNS Failure The message bounced 1) Traditional Bounce codes 2) Enhanced bounce codes What is Traditional Bounce code? The traditional bounce codes are a type of SMTP status codes. It indicates that the email was rejected due to permanent issues encountered by the remote server. ESPs translate the actual SMTP codes and diagnostic messages into their own internal categories to simplify bounce reporting for users. Each error corresponds to a specific SMTP response with a unique Category, Error Code and Status Code. Aug 27, 2024 · A bounce response from a mailbox provider typically includes 3 key elements that help identify the cause of the rejection: a basic SMTP status code, an enhanced SMTP status code, and a text description. Feb 15, 2023 · SMTP codes can be confusing but they hold important information about the status of your email delivery. Each email bounce comes with such a cryptic code that marketers need to troubleshoot to ensure smooth future deliveries. Bounce Handling System: An email marketing platform automatically processes bounce messages received from mail servers, categorizes bounce types based on SMTP bounce codes, and updates subscriber lists accordingly, removing invalid or undeliverable email addresses to improve deliverability. Account Engagement doesn’t generate bounce codes, so contact the recipient’s mail server administrator if you need clarification about a Feb 1, 2015 · The 5. Aug 13, 2025 · When encountering a hard bounce for an address you believe is valid, your first step should always be to consult the bounce logs provided by your email service provider. 0 (SMTP reply matched bounce-rcpt pattern rule)]" is often an interpretation provided by your Email Service Provider. Dec 17, 2024 · Have you ever run into the SMTP bounce message "too old"? Perhaps with a status code of 602? Here's what that means! This isn't an SMTP rejection code enshrined in the RFC covering email rejection and deferral codes. an example will be 550. Addressing SMTP bounce codes The exact code number is customized by each Internet service provider. Learn about the most common codes and what they mean. SMTP (Simple Mail Transfer Protocol) defines this code, and it's your only clue as to why your message was rejected. Enhanced SMTP Codes Traditional SMTP Codes These are three-digit codes that provide basic information on delivery success or failure. Aug 9, 2023 · Email bounce codes are automated responses from a recipient's mail server, providing reasons for the non-delivery of an email you sent. These codes are generated by the recipient's email server or the receiving email service provider. Aug 22, 2024 · We'll explore some of the most common email bounce codes, what they mean, and how you can resolve the issues that cause them. Why it matters: who’s speaking changes how reliable the diagnosis is. Alias_address - (valid) These email addresses act as forwarders/aliases and are not real inboxes. You can review our list of SMTP error messages below for details about each error. Traditional SMTP Bounce Codes Traditional SMTP bounce codes are three-digit numbers (e. Mar 28, 2024 · Hard bounces are typically a 500 bounce code, or a bounce code that starts with a 5 such as 5. cloud client, and a rule is triggered by the email recipient's configuration. That’s the X. Jun 12, 2023 · What Are Email Bounce Codes? Email bounce codes are three-digit numbers that indicate the reason for an email's failure to reach the recipient. This guide will help you understand common SMTP bounce codes, diagnose the cause, and take action to resolve the issues efficiently. The messages and codes can help you troubleshoot and resolve email delivery problems. Enhanced SMTP bounce codes vs. Apr 15, 2025 · Understand what causes '550 relaying denied' bounce errors and learn how to diagnose and resolve them, focusing on authentication, DNS, and server configuration. SMTP Status Code— The SMTP enhanced status code, as defined by RFC 3463. Y. Enhanced SMTP error codes – with dots, e. Hard […] Email bounces and explanation of bounce codes When you, as a customer at MarketingPlatform, send an email to a contact, a response will be sent back from the recipient’s mail server to MarketingPlatform’s mail server. Apr 30, 2025 · Understand email bounce and block codes with our comprehensive guide. Enhanced SMTP Bounce Codes Enhanced email bounce codes provide more detailed information about email delivery failures. Jan 2, 2024 · Bounces The bounce event extract file shows all the hard and soft bounces that occurred in a specific date range. Below is a list of the Standard SMTP error codes and the Extended SMTP (ESMTP) error codes. Nov 13, 2023 · This article will help you understand the different reasons for email bounces and error codes. Jul 25, 2025 · The anatomy of a bounce message Every email bounce message typically consists of three distinct parts, each offering a different level of detail about the delivery failure. Oct 21, 2024 · A "Mailbox Full" bounce occurs when the recipient's inbox has reached its storage limit and cannot accept new messages. Nov 17, 2023 · Learn what Standard SMTP error codes and the Extended SMTP (ESMTP) error codes mean for email bounce diagnostics. Codes in the 400 range are generally Soft Bounces Codes in Jul 29, 2025 · Learn what causes the 550 5. 4xx codes (temporary failures / soft bounces): These codes indicate a temporary problem, and usually means the sender can try sending the message to the recipient again. Below is a screenshot comparing both. Plus steps and strategies to manage and to cut down on bounces. May 23, 2023 · Dive into the world of email bounce status codes and gain a deep understanding of the different types, causes, and solutions for email delivery issues. Master SMTP error codes to enhance email deliverability, reduce bounces, and maintain a strong sender reputation effortlessly. Sometimes the message is accepted, then bounces downstream (intermediate relay, internal rule). Learn SMTP, Enhanced Status Codes, and how to fix deliverability issues with our complete guide. Transport of Electronic Mail The objective of the Simple Mail Transfer Protocol (SMTP) is to transfer mail reliably and efficiently. Traditional Soft Bounce Codes Traditional Hard SenderScore's email bounce error guide to help you troubleshoot and fix email error code 4. Sometimes, these codes Oct 18, 2025 · Understand email bounce error codes like 550, 421, and 554 — learn why emails fail and how to fix them for better deliverability. May 29, 2008 · Simple Mail Transfer Protocol (SMTP) Enhanced Status Codes Registry Created 2008-05-29 Last Updated 2024-12-06 Available Formats XML HTML Plain text Registries Included Below Class Sub-Codes Subject Sub-Codes Enumerated Status Codes Class Sub-Codes Registration Procedure (s) Specification Required Expert (s) Chris Newman Reference [RFC5248 What Are Email Bounces? An email bounce occurs when an email you send fails to reach the intended recipient. When a Remote-MTA rejects a message during an SMTP transaction, a field Diagnostic-Code of type smtp may be used to report that value. Common Bounce Codes A bounce code is a reply from the recipient’s mail server that describes why an email wasn’t delivered. Soft bounces (4xx codes): Temporary failure. Reply Sender— The email address of the sender of the bounced email. g. See Google's list of Gmail SMTP errors and codes. Si la entrega no se ha realizado correctamente, los códigos indican el motivo. View valid values for SMTP reply codes (GreenEnd). e. Portrait Dialogue handles all replies to the reply address configured in Bounce email setup with this functionality. Aug 13, 2025 · Later, in a DSN (bounce message). What’s better than knowing how to read secret codes, right? You decode, understand, and find problems and solutions, all in the interest of successful delivery of your emails. Mail server administrators can customize bounce code messages. In this method, the three digit codes are separated by decimal points. 2. (5. Note:See Microsoft’s and Google’s documentation for additional bounce codes if Jul 1, 2025 · Learn how to get SMTP bounce messages from Salesforce Marketing Cloud (SFMC) to improve email deliverability and maintain sender reputation. Message— Human-readable text to include in the bounce email. May 5, 2025 · Discover how email service providers (ESPs) handle soft and hard bounces, interpret bounce codes, and apply soft bounce tolerance to protect sender reputation and optimize deliverability. Dec 20, 2021 · Not all bounce codes are as straightforward as the example above—but we’re here to help you make sense of them all. Aug 9, 2025 · Learn which SMTP bounce codes indicate permanent failures (hard bounces) and should lead to immediate mailing list suppression, and how to manage temporary (soft) bounces to maintain a healthy sender reputation. If you receive an email bounce, you can look in the bounce message to find the proper error code that will give you the reason for the bounce. Enhanced SMTP Bounce Codes vs. The bounce code in Portrait Dialogue's Dialogue Admin is different from SMTP bounce codes. Introduction 1. Overview There is a need for a standard mechanism for the reporting of mail system errors richer than the limited set offered by SMTP and the system specific text descriptions sent in mail messages. RFC 3463 Enhanced Mail System Status Codes January 2003 1. Here is a comprehensive guide to Oct 30, 2024 · Understanding SMTP bounce codes, their meanings, and how they impact email delivery. This is the address from which the bounce email will be sent. Jan 6, 2024 · These codes reveal temporary bounce errors and permanent or more severe issues with email delivery. aawiib nfzjgdu xnqme pen awxw wahfsy lxxqu bjobvv huq qbu kutuq gpq dwxwmz rjkan dbfelr