Why are emails hard bouncing then opening and clicking links later?

Emails can hard bounce initially but still register opens and clicks later due to a complex interplay of factors. These include delayed bounces triggering content/link scanners, VERP configuration issues, inaccurate bounce categorization, filter soft rejections followed by retries, nuanced rejection points (connect/helo, mail from, rcpt to, data), greylisting practices, asynchronous bounce processing in services like AWS SES, temporary server unavailability, and prefetching of links. Security software and spam filters can trigger opens and clicks even without actual user interaction. Underlying this behavior are technical factors such as SMTP error codes allowing for retries and the implementation of deferred delivery by MTAs. Errors in reporting and initial blocking with subsequent acceptance also contribute to the phenomenon. Understanding the nuances of SMTP standards, bounce processing, security software impact, and greylisting is crucial for accurate interpretation of email deliverability metrics.

Emails might hard bounce initially but still register opens and clicks due to several reasons. These include delayed bounces and subsequent scanning by content/link scanners, inaccurate bounce categorization by ESPs, greylisting delaying delivery, security software triggering events before inbox delivery, delayed processing of bounce messages, errors in bounce reporting, prefetching of links by email clients, interaction of spam filters with email content, and temporary server unavailability followed by successful retry. Therefore, a hard bounce followed by opens/clicks does not necessarily indicate an error, but requires careful interpretation of bounce data and server behavior.

Emails experiencing hard bounces followed by opens and clicks can stem from several underlying causes. These include VERP implementation issues where spam to the bounce address is misclassified, general problems with reporting and bounce management, soft rejections by filters after data transmission followed by successful retries, the nuances of different rejection points (connect/helo, mail from, rcpt to, data), initial blocking and subsequent acceptance after retries, and greylisting practices causing temporary rejections. Essentially, such behavior highlights the complexity of email delivery, requiring careful attention to configuration, reporting, and transient server behavior.

Emails hard bouncing then registering opens/clicks can be attributed to several technical factors. Servers might initially issue a 5xx error but later accept delivery due to improved conditions or retries, as defined in SMTP standards. Mail transfer agents like Postfix implement deferred delivery, retrying bounced messages successfully later. Security features like Microsoft's Safe Links scan URLs and register clicks despite eventual blocking. Asynchronous bounce processing, particularly in services like AWS SES, can lead to opens/clicks registering before bounce notifications. Finally, transient SMTP failures, according to IETF standards, prompt automated retries that might succeed.