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

Email marketer from Campaign Monitor explains that if a receiving server is temporarily unavailable and subsequently available after a retry, the email may get delivered. It results in opens/clicks after the initial bounce report.

Email marketer from EmailOnAcid shares that security software can trigger opens and clicks before the email reaches the inbox. If the email hard bounces and the security software scanned it, this behavior may occur.

Email marketer from Reddit suggests that the issue might be due to greylisting. The receiving server temporarily rejects the email, then accepts it on a retry. The initial rejection may register as a hard bounce.

Email marketer from Litmus explains that a recipient's email client might prefetch links. This will result in recorded link clicks before the email has actually been opened or read by the end user.

Email marketer from Quora proposes that there might be errors in how the sending platform reports bounces. A temporary server issue could be logged as a hard bounce, while the email is ultimately delivered.

Marketer from Email Geeks suggests that if the bounces are delayed, clicks/opens can be triggered by content/link scanners.

Email marketer from SendGrid Help Center explains that bounce categorization can sometimes be inaccurate. A temporary issue might be misclassified as a hard bounce, and if the issue resolves quickly, the email might still be delivered and interacted with.

Email marketer from StackOverflow suggests that sometimes there can be a delay in processing bounce messages. The open and click events might be registered before the bounce status is fully processed and updated in the system.

Email marketer from SparkPost indicates that spam filters could interact with the email content. This triggers link clicks and potentially open events, even if the message is not ultimately delivered to the recipient's inbox.

Email marketer from Mailjet Help Center explains that this can happen if a recipient's server initially rejects the email (hard bounce) but later accepts it, possibly after a retry. The open/click could be due to the email eventually reaching the inbox or being scanned by security software.

Expert from Email Geeks mentions that rejections on connect/helo, mail from, rcpt to, and data can all have different meanings, highlighting the complexity of bounce reasons.

Expert from Email Geeks suggests that multiple hard bounces on the same email address indicate issues with reporting or bounce management, and recommends investigating further.

Expert from Spam Resource explains that one reason is greylisting, where servers temporarily reject emails from unfamiliar sources, then accept them after a retry, leading to delayed delivery and potentially opens after an initial bounce.

Expert from Word to the Wise explains that it could be a result of initial blocking followed by acceptance on a retry. This would result in an email first being blocked before eventually going through.

Expert from Email Geeks shares an experience where a filter soft rejected mail after DATA, holding it in a queue for 2 hours. During this time, link clicks and image pixel loading were observed. The message was accepted on the second delivery attempt.

Expert from Email Geeks explains that when using VERP, spam sent to the bounce address can be counted as a hard bounce incorrectly. Recommends parsing to ensure it's a real NDR or expiring VERP addresses after sending.

Documentation from RFC Editor details SMTP error codes, including temporary (4xx) and permanent (5xx) failures. A server might initially return a 5xx error but, due to network conditions or configuration changes, later accept a re-attempted delivery. Opens/clicks would then be registered.

Documentation from Postfix.org explains that Postfix, a mail transfer agent, implements deferred delivery. If a message initially bounces, Postfix will attempt to deliver it again later. If the later attempt succeeds, the message is delivered, and the user may open and click links.

Documentation from IETF defines transient SMTP failures. Some systems are designed to automatically retry sending an email. The retries could succeed in the time between the hard bounce occurring and the system logging the open/click.

Documentation from Microsoft explains that the Safe Links feature in Microsoft Defender scans URLs in emails. This scan can trigger a click event even if the email is eventually blocked or bounced due to another issue.

Documentation from AWS explains that using services like SES (Simple Email Service), the bounce processing can sometimes be asynchronous. Meaning that the system could register opens/clicks before fully processing the bounce notification.