Why is there a sudden spike in Yahoo 'mailbox not found' bounce rates?

Email marketer from EmailDrip Help Center suggests that Yahoo may be implementing stricter email validation processes, leading to more rejections of potentially risky or low-quality email addresses.

Email marketer from SendGrid shares that the best way to improve your email marketing list health is to ensure you are only sending emails to people that want to receive them. By doing this you will prevent high bounce rates.

Email marketer from Email on Acid shares that the more you send to these addresses, the more your sender reputation will suffer. The best way to prevent list degradation is to start with a clean, permission-based list and practice regular list hygiene.

Marketer from Email Geeks reports seeing a lift in hard bounces, but notes it's with a new client and the age of the subscriber data is unknown.

Email marketer from MailerLite Help Center indicates that Yahoo periodically purges inactive accounts. If subscribers haven't engaged with emails in a while, their accounts might be deactivated, causing 'mailbox not found' errors.

Email marketer from StackOverflow suggests the mailbox may have been disabled due to spam complaints, inactivity, or policy violation.

Email marketer from Reddit suggests that a sudden increase in bounce rates could be due to a recent change in Yahoo's spam filtering or account handling procedures. They also suggest checking your sender reputation.

Marketer from Email Geeks shares that there appears to be a spike in bounce rates across the board, even with inboxes considered 30-day openers, and that Yahoo seems to do these purges a few times a year.

Email marketer from Litmus shares that it's better to try and get unengaged subscribers to resubscribe or unsubscribe to help improve your email deliverability and bounce rates.

Expert from Spam Resource emphasizes that maintaining a high-quality email list is critical. Sudden spikes in bounces, including 'mailbox not found' errors, can be caused by sending to old, unengaged addresses, or those obtained through questionable means. Regular list cleaning and validation are essential to minimize these issues.

Expert from Word to the Wise shares that good list hygiene is important to reduce bounces. This includes removing unengaged users who have not clicked on any emails after a certain time.

Documentation from Google shows that authenticating emails and keeping your spam rate low will ensure more emails are delivered to mailboxes.

Documentation from Validity (formerly ReturnPath) explains that a poor sender reputation can lead to higher bounce rates and reduced deliverability. This can occur if Yahoo perceives your email practices as spammy or untrustworthy.

Documentation from Microsoft suggests that bounce messages or Non-Delivery Reports (NDRs) from email servers such as Yahoo indicate an issue when the recipient's email server won't accept the message.

Documentation from Spamhaus suggests that maintaining a clean list, using double opt-in, and regularly removing inactive subscribers are key to preventing hard bounces.

Documentation from RFC Editor specifies that '550 Requested action not taken: mailbox unavailable' (or similar) indicates that the mailbox doesn't exist or the server refuses to forward mail to it.