Why don't mailbox providers publish detailed bounce message explanations?

Email marketer from StackExchange believes the reasons are that there are way too many scenarios for bounces (and there are no agreed-upon standards for it) and email providers don't want to provide spammers with possible hints.

Email marketer from EmailDeliveryJunkies explains that obfuscation is implemented to keep the information away from email spammers. Specific error information makes it easier for bad actors to exploit systems.

Marketer from Email Geeks shares the frustration that 99% of the time when someone provides a bounce and asks what the problem is, they effectively repeat the content of the bounce to them, and somehow they now understand it.

Email marketer from Mailtrap.io explains that SMTP bounce codes, though seemingly cryptic, follow a standard format but providers want to maintain a degree of ambiguity to prevent malicious actors from exploiting detailed information about their filtering mechanisms. This lack of detail can hinder legitimate senders, but it is thought to be a necessary evil.

Email marketer from StackOverflow suggests that bounce messages are deliberately vague to prevent spammers from adapting their techniques. More specific error messages would give spammers valuable information about what triggered the bounce, allowing them to refine their methods to bypass filters.

Email marketer from Super User mentions that while there are some messages that are easy to understand, the problem is that spammers would love to have the information too.

Email marketer from mailsend.in explains that mailbox providers might not publish detailed explanations due to the complexity of bounce messages, which can vary based on numerous factors. Also the desire to prevent spammers from gaming the system and that constantly changing infrastructure/spam filters makes it difficult.

Email marketer from SendPulse shares that the providers would need to keep updating the explanations constantly and spammers would learn the ins and outs of their systems to take advantage of them.

Email marketer from Reddit notes that a likely reason for the lack of publicly available bounce documentation is so that spammers do not know exactly what they are doing wrong.

Expert from Email Geeks explains that most bounce messages are self-explanatory if read carefully. Many people refuse to answer questions about bounces without the specific message, because the messages often clearly state the issue.

Expert from Email Geeks explains that a lot of postmaster teams are under-resourced, and website teams have different priorities than SMTP teams, making publishing bounce explanations a low priority. Also, people often ignore published information anyway.

Expert from Email Geeks suspects that the IT group has no actual skills, and unless they can find an answer in their local knowledgebase their sole escalation approach is to ask someone else to do the work for them.

Expert from Word to the Wise explains that providers would have to keep updating explanations constantly and spammers would learn the ins and outs of their systems to take advantage of them. They go on to share how a 5xx error usually indicates permanent failure.

Expert from Email Geeks explains that a "501 Syntax error in parameters or arguments" means you’re violating SMTP by sending illegal commands, most likely because your pipelining is broken, you ignored a previous error response, or you’re trying to mail something that’s not an email address.

Expert from Email Geeks explains that the SMTP RFCs specify what the response codes mean, at least to a category, and many MBPs respond with tokens that can be cross-referenced with their postmaster pages or searched online. Others include URLs or human-readable explanations. However, sometimes the MBP is intentionally vague, even then.

Expert from Email Geeks explains that people don’t read the existing, clear explanations, and what’s needed isn’t a FAQ, so much as it’s training and professional standards. An explanation of how to read a rejection code would potentially be part of that training.

Expert from Word to the Wise shares that bounce messages often contain enough detail to diagnose issues, suggesting the problem is often in understanding the available information rather than a lack of detail. Senders need to understand how to interpret them.

Documentation from Google Support explains that to protect their users from spam and abuse, they obscure full reason codes. It is more important to prevent the bad actors from gaining additional insight into what the trigger was.

Documentation from RFC 5321 explains that SMTP reply codes are designed to provide a general indication of the outcome of a request, but detailed explanations are not included because the specific reasons for failure can vary widely and are often implementation-specific. The RFC defines the categories of errors, but not the granular details.

Documentation from IONOS explains that various reasons may cause an email bounce. The lack of detailed explanations is because the specifics are often technical and subject to change, and also there is an element of obscurity for security reasons.

Documentation from Microsoft Learn answers questions about the specifics of why an email wasn't delivered. In general, these non-delivery reports have codes and short summaries. It is important to protect their backend systems from spammers.