What does 'exceeded allowable posts without captcha' mean in a bounce message?
Summary
What email marketers say9Marketer opinions
Email marketer from StackExchange describes that the bounce message indicates the recipient mail server has blocked the messages as the sender hasn't proven it's human through a CAPTCHA after sending a certain amount of mail.
Email marketer from MXToolbox shares that it indicates the recipient server is blocking emails because the sender's activity looks suspicious, like an automated bot sending emails without CAPTCHA verification.
Email marketer from Mailjet details that a bounce message like this generally indicates that the receiving server has detected the sending server is exhibiting bot like behaviour by not using captchas and that limits have been reached.
Email marketer from Email Provider Forum answers that the error message signifies the server is implementing rate limiting to prevent abuse, requiring a CAPTCHA to allow further sending after a certain threshold.
Email marketer from Quora shares that the message suggests the sending server's IP might have been flagged for suspicious activity, and the recipient server requires a CAPTCHA to verify the sender’s legitimacy to combat spam.
Email marketer from Email Marketing Blog explains that it suggests that you are sending too many emails without proving you are not a bot. Implement CAPTCHAs to allow users to prove their legitimacy.
Email marketer from Reddit shares that this bounce message likely means the sending server has hit a limit on sending emails without solving a CAPTCHA to verify it's not a bot. It’s a security measure to prevent spam.
Email marketer from Email Deliverability Blog answers that the message means the receiving mail server is requiring sender authentication to avoid being treated like SPAM.
Email marketer from Senderlist explains that a 'exceeded allowable posts without captcha' error means you need to configure captcha on your website.
What the experts say3Expert opinions
Expert from Word to the Wise explains that exceeding allowable posts without captcha is often related to sender reputation and the authentication process. The recipient server detected a lack of human verification.
Expert from Spam Resource explains that this bounce message indicates that the server suspects you are sending automated emails and you must prove you are a real person with CAPTCHAs.
Expert from Email Geeks shares an example of a bounce message: 5.0.0 smtp; You have exceeded the allowable number of posts without solving a captcha.
What the documentation says4Technical articles
Documentation from Postmark describes a 5.0.0 error as a general failure. In this context, Postmark may rate limit mail based on trust/authentication or lack of captcha verification.
Documentation from AWS SES explains that a 5.0.0 error usually indicates a permanent failure, which may be the result of the recipient server imposing restrictions on unverified senders. Using CAPTCHAs would bypass this.
Documentation from Microsoft Learn explains that a 5.0.0 SMTP error often indicates a generic delivery failure. In the context of exceeding allowable posts without a CAPTCHA, it implies the mail server rejected the message due to suspected automated activity.
Documentation from RFC explains that a 5.X.X code is a permanent failure. In the context of CAPTCHAs, the sending server would have been blocked due to rate limits due to suspected bot like behaviour.