550 mailbox unavailable

The infamous "550 Mailbox unavailable" error!

This error typically occurs when the recipient's email account is full, disabled, or not set up correctly, preventing the email from being delivered. Here are some possible reasons and solutions:

  1. Recipient's mailbox is full: If the recipient's mailbox is full, they won't be able to receive new emails. Ask them to delete some emails or upgrade their mailbox size.
  2. Recipient's email account is disabled: If the recipient's email account is disabled, they won't be able to receive emails. Check with the email provider or administrator to see if the account is disabled and if it can be reactivated.
  3. Recipient's email account is not set up correctly: If the recipient's email account is not set up correctly, emails may not be delivered. Check the recipient's email settings to ensure they are correct.
  4. Email server issues: If there are issues with the email server, emails may not be delivered. Check with the email provider or administrator to see if there are any known issues or outages.
  5. Spam filters: If the recipient's email account has strict spam filters, emails may be blocked or marked as spam. Ask the recipient to check their spam filters and whitelist your email address.

To troubleshoot the issue, you can try the following:

  1. Check the recipient's email account: Log in to the recipient's email account to see if the email is stuck in their inbox or if there are any error messages.
  2. Check the email headers: Check the email headers to see if there are any errors or issues with the email delivery.
  3. Try sending a test email: Send a test email to the recipient to see if it's delivered successfully.
  4. Contact the email provider or administrator: If none of the above steps work, contact the email provider or administrator to see if they can help resolve the issue.