What does a Gmail bounce message look like for exceeding the spam complaint rate?

Email marketer from Email Geeks explains that neither the spam thresholds, nor the treatment of senders who regularly exceed them are new and that what’s new is just us talking about it and being a bit more transparent and that you should already have run into problems delivering emails (and gotten appropriate SMTP responses) in the past (even below 0.3%).

Email marketer from StackExchange explains that a bounce message like '550 5.7.1 Rejected: Message blocked due to spam content in the message's body' is unlikely due to spam compliants however spam complaints can lead to a similar outcome. To resolve this improve the content of the email and/or review your email practices.

Email marketer from Reddit shares that if a message is failing due to spam the result of that would be your domain being added to a blacklist and future messages failing with an error 500 or 550 response code.

Email marketer from Email Geeks shares they have seen clients get rate-limited for an "unusual rate of unsolicited mail" when their complaint rate is above 0.3%.

Email marketer from Postmark details understanding different types of email bounces, hard bounces and soft bounces. While not directly mentioning 'spam complaint rate', they say soft bounces (like '4XX' errors) could temporarily result from reputation issues linked to complaints. They recommend monitoring bounce rates to stay below thresholds.

Email marketer from SparkPost shares details on what to do to avoid spam filters. While not directly answering the question, it does provide the outcome. Email blocked with codes like '550 5.7.1' can result in the inability to send emails and your IP address or domain name is added to a blocklist.

Email marketer from SocketLabs notes how email reputation effects deliverability. Being marked as spam will affect sender reputation which will be reflected in spam filters and cause deliverability issues.

Email marketer from Mailjet shares that seeing a bounce message like '550 5.7.1 Service unavailable; Client host [IP address] blocked using Spamhaus' means your IP has a poor reputation, usually related to spam complaints or low email engagement. The action to take is to improve your sender reputation by only mailing engaged users.

Email marketer from WPForms shares how to improve email deliverability. This includes how to avoid the spam folder with a low spam rate and how to avoid being added to blacklists.

Email marketer from MailerQ shares that SMTP errors are returned when there is a problem with the deliverability of the email. They share the common codes with 5xx errors indicating a permanent error. In the case of spam, this might include error code 550 5.7.1

Expert from Email Geeks confirms this rate limiting is not new and the deferral message that's expected if you were enough of a problem source to get deferred.

Expert from Word to the Wise explains that hitting spam traps can lead to blocking and deferred emails, including those with SMTP error codes indicating a reputation problem. While not directly related to the complaint rate, this falls in line with what could happen if you exceed it.

Expert from Email Geeks suggests that if Gmail bounces emails due to spam complaints, the bounce message would likely indicate that 'the domain has a low enough reputation that we suspect this message is spam'.

Expert from Email Geeks explains that Gmail probably doesn't reject emails with a 'this mail is malformed' message when exceeding the 0.3% spam complaint rate. Instead, it's more likely that emails will end up in the spam folder if the spam complaint rate is consistently high.

Expert from Spam Resource explains the importance of sender reputation when sending emails. Without a good sender reputation, email is much more likely to go to the spam folder or be blocked altogether, returning errors related to spam and sender reputation issues.

Documentation from Google Support explains that Gmail may bounce messages with an error like '550 5.7.1 Spamhaus' if the sender's IP address or domain is listed on a known spam blacklist. This isn't directly a 'spam complaint rate' message but an indicator of spam-like characteristics.

Documentation from RFC 3463 (an older RFC, still relevant for bounce codes) documents enhance mail system status codes. While it doesn't specifically mention a 'spam complaint rate' bounce code, it details the structure of bounce codes (5.X.X for permanent failures) which is used to indicate problems like policy rejections, which spam complaints would fall under.

Documentation from Microsoft highlights the format of SMTP ETRs and provides multiple real world examples. The ETR itself should provide a deeper and more technical explination of why emails are rejected to the sender. Common reasons being blacklisting or complaints.

Documentation from Sendgrid shares common bounce reasons related to spam. The example errors include; Suspicion of spam, the mail server sees the message as spam-like and the action is to review your content and email sending practices.

Documentation from Spamhaus explains the result of being blocked by spam, an example is; 'blocked using Spamhaus' that is triggered by excessive spam complaints or spam-like sending behavior. It results in your emails being blocked or deferred by recipients.