What causes Hotmail 550 5.5.0 mailbox unavailable bounce errors?

Email marketer from EmailDudes Forum states that the 550 5.5.0 error can mean a number of things, including the recipient's mailbox being full, the account being inactive, or a typo in the email address. They recommend verifying the email address and trying again.

Email marketer from Stack Overflow shares that the error means the mailbox is unavailable. Reasons can include that the mailbox doesn't exist (typo in address), the user account is inactive, or the mailbox is full and cannot accept new messages. Also possible the sending IP is blocked.

Email marketer from Reddit shares that a common cause is an inactive or non-existent email address. This is often due to users abandoning old accounts. Also possible the sending IP is blocked.

Email marketer from Stack Overflow explains that a 550 5.5.0 SMTP error indicates that the email address doesn't exist on the recipient's mail server or the recipient's mailbox is inactive. Also possible the account has been suspended. It is a permanent failure.

Email marketer from MailerQ Documentation says that the 550 5.5.0 error from Hotmail can indicate issues with your sending reputation, potentially due to spam complaints. Review your sending practices and reputation metrics.

Email marketer from Super User says 550 errors normally mean that the email address does not exist.

Email marketer from Email Marketing Tips Forum suggests that problems with Hotmail and Outlook could be related to Microsoft's SmartScreen filter. If your email content triggers the filter, Hotmail could return a 'mailbox unavailable' error. Look at your content, and try sending the email again.

Email marketer from Quora suggests that if you are getting the '550 5.5.0' error from Hotmail and you've checked the email address, it might indicate your IP address or domain is blacklisted. Check your IP and domain reputation to find out.

Email marketer from Reddit suggests that the 550 5.5.0 bounce error is often due to an invalid email address. Double check the spelling and try sending again. If the problem persists, the mailbox may be full, or the user no longer exists.

Expert from Word to the Wise notes that 550 errors are permanent failures, meaning the message cannot be delivered to that recipient. 5.5.0 often means the recipient mailbox doesn’t exist on the mail server or the recipient’s mailbox is inactive.

Expert from Email Geeks explains that mailbox unavailable is usually not spam related. Hotmail often loses sync between the MTAs and backend database, causing this bounce error.

Expert from SpamResource explains that 550 errors generally indicate that the server refuses to accept the mail. A 5.5.0 code commonly indicates that the recipient address does not exist.

Documentation from Microsoft Support explains that the 550 5.5.0 error is a general permanent failure. It usually means the recipient's email address doesn't exist. Double-check the recipient's email address for typos and ensure it's correct.

Documentation from RFC Editor explains that 5.X.X status codes indicates a permanent failure. The message should not be sent again. Specifically, the 5.5.0 code indicates that the address is invalid for the mailbox.

Documentation from AWS states that a 5.5.0 SMTP code specifies that the email address does not exist, or the mailbox is unavailable. Check the email address exists and you are not blocked.

Documentation from Exim.org explains that 550 errors are permanent failures. A 550 5.5.0 typically means the recipient's mailbox is unavailable for policy reasons. Check the specific error message from the mail server for more details.

Documentation from cPanel says 550 errors are usually due to an invalid email address or a problem with the recipient's server. Verify the recipient's email address and try again later.