Why does an email bounce after being opened multiple times?

Email Marketer from Email Geeks suggests to check the detailed MTA logs: it's likely that first attempt was greylisted, and the filter reviewed the content and made a decision before the reattempt.

Email marketer from SendPulse shares that Hard bounces indicate a permanent reason an email cannot be delivered and typically results from invalid email addresses. An address that was once valid may become invalid over time. While they don't explicitly explain multiple opens before a bounce, a hard bounce could be triggered after a system re-validates the email on subsequent interactions (opens).

Email marketer from Reddit explains that some email providers perform real-time analysis of URLs and content. If an email is initially allowed but a subsequent analysis (triggered by an open) flags a malicious link or content, the server might retroactively bounce the email.

Email marketer from Neil Patel Digital explains that high bounce rates can occur if spam filters are triggered. Although not directly addressing opens, it implies that if an email triggers a spam filter after being opened (due to content, links, etc.), it can contribute to bounces.

Marketer from Email Geeks explains that the 'opens' being measured are likely just asset downloads. A machine may download the email's assets and then bounce it.

Email marketer from Gmass Help Center explains that Spam filters may analyze the engagement with an email over time. If an email is opened multiple times but has low engagement (no clicks, replies), it could be flagged as suspicious, increasing the likelihood of future bounces.

Email Marketer from Mailgun Help Center explains that a possible cause for bounces after opens is that a security filter or anti-virus software might be opening the email and clicking links before marking it as spam, causing the bounce.

Email marketer from Stack Overflow shares that monitoring tools may be implemented by recieving mail servers, if an email is viewed and links are clicked, there may be systems in place to ensure the URL's are not malicious, these systems could then initiate a bounce to prevent further opens and link clicks.

Email marketer from Quora suggests that delayed greylisting may occur. The receiving server might initially accept the email, but delayed checks mark it as spam, leading to a bounce. This may occur after opens trigger a re-evaluation of the content.

Email Marketer from ActiveCampaign details that bounces happen as there are invalid addresses due to typos, fake emails, or addresses that no longer exist. While the article doesn't directly address opening before a bounce, an email address can transition to invalid from valid and this could lead to a delayed bounce when a campaign is sent to it.

Email Marketer from Litmus details that bounces are a key indicator of email list health. Although the article doesn't directly address opening before a bounce, it's feasible that an email address transitions from valid to invalid or spam trap after initial opens, leading to a bounce later.

Expert from Email Geeks suggests that a remote host may receive the content, check the links, and then reject it after the DATA transfer.

Expert from Email Geeks explains some places see the whole message before they accept it for delivery. Some places do temp failures after DATA - but they can keep a copy of the message and evaluate it and then accept it when it's attempted for redelivery.

Expert from Word to the Wise explains that emails can be filtered and blocked after delivery if their content is deemed inappropriate, leading to a bounce. The content becomes an issue after it's been delivered.

Expert from Email Geeks shares that a filtering system can bounce a message back to the sender, even after it has been viewed. Also a human could have looked at your email and then blocked the sender and sent a bounce response back.

Expert from Spam Resource explains that bounces can occur if the sending server's IP address is added to a blocklist after the initial email send but before subsequent attempts. Initial opens don't trigger the blocklisting, but the blocklisting then causes the bounces.

Documentation from RFC Editor details that temporary failures (4xx errors) can occur after the DATA command, indicating that the server has accepted the message content but is unable to deliver it immediately. This could happen due to various reasons, including content filtering or greylisting.

Documentation from AWS states that bounces occur for permanent or temporary reasons. Feedback loops, where recipients mark emails as spam, contribute to bounce rates. It's conceivable that a user initially opens an email but then marks it as spam, leading to subsequent bounces to the sender.

Documentation from Google Postmaster Tools states that high spam rates directly impact deliverability. If users repeatedly open an email but consistently mark it as spam, Gmail might start bouncing emails from that sender to protect its users.

Documentation from Spamhaus explains that being listed on a blocklist is a common cause for email bounces. Although not directly related to opens, it is possible that initial emails are allowed, but after analysis from behaviour (opening the email), it triggers the spamhaus blocklist causing subsequent bounces.

Documentation from Microsoft Support details that Exchange Online Protection uses various methods to help prevent spam from reaching users. It's possible that an email is initially allowed but later flagged as spam based on content or sender reputation after being opened, leading to a bounce on subsequent interactions.