Why are emails hard bouncing with 'The email account does not exist' after previously being opened and received?

Email marketer from EmailOctopus Blog suggests that if previously valid email addresses are now hard bouncing, it could be due to the recipient's email account being closed or deactivated. Email providers recycle these addresses as spam traps. Continously sending to these addresses will harm your sender reputation.

Email marketer from Reddit explains that ISPs will often recycle old email addresses into spam traps. An old, valid address that has since lapsed can begin causing hard bounces if not cleaned from the list.

Marketer from Email Geeks asks if they were previously soft bouncing because storage was full and they’ve been deactivating a lot of those this year.

Email marketer from GMass Blog shares that a 'user unknown' hard bounce could indicate the email address existed at one point but has since been deleted. Providers sometimes recycle these addresses. Frequent sending to old addresses will harm reputation.

Marketer from Email Geeks shares Google has begun enforcing 2 key policies, one regarding non-activity in 2 years, another regarding account storage being full and this could be the follow up message to those that come when someone hasn’t engaged in 2years and gets cut off.

Email marketer from Mailjet explains hard bounces occur when an email address is invalid, the domain name doesn’t exist, or the recipient server has completely blocked delivery. Senders need to remove hard bounces immediately to improve sender reputation.

Email marketer from ActiveCampaign shares that sudden hard bounces for previously engaged contacts may mean those addresses are now inactive or have been converted into spam traps by ISPs to catch spammers. Regular list cleaning is essential.

Email marketer from Neil Patel's Blog explains that hard bounces indicate an invalid or non-existent email address. Maintaining a clean email list through regular scrubbing is crucial to avoid sending emails to such addresses and damaging your sender reputation. This is especially important as stale addresses can become recycled into spam traps.

Email marketer from Constant Contact states a hard bounce is a permanent delivery failure, often because the email address is invalid or does not exist. These should be immediately removed from contact lists to preserve sender reputation.

Email marketer from StackExchange explains hard bounces that follow prior engagement can be due to account deletion, domain issues or aggressive spam filtering changes. Sender reputation management is critical.

Expert from Word to the Wise (Laura Atkins) explains that expired or abandoned email addresses can be turned into spam traps by mailbox providers. If previously valid addresses are now hard bouncing, those addresses may have been converted into spam traps. Good list hygiene practices are vital.

Expert from Spam Resource (John Levine) explains that some ISPs recycle email addresses. When an account is abandoned, the address might eventually be turned into a spam trap. Sending to that address will result in a hard bounce, but also potentially hurt your sending reputation.

Documentation from RFC Editor explains that SMTP error code 550 (and related codes) often signify 'mailbox unavailable' or 'user unknown', indicating the email address is no longer valid on the receiving server. It is a permanent failure.

Documentation from Amazon Web Services explains a hard bounce indicates the email address is invalid. Common causes include the domain doesn't exist or the recipient is unknown. A best practice is to immediately remove the hard bounce from your list to protect your sending reputation.

Documentation from SendGrid explains a hard bounce signifies a permanent reason an email cannot be delivered, such as a non-existent email address. Repeatedly sending to hard bounces can negatively impact your sender reputation. Address these bounces by immediately removing the addresses from your contact list.