Sometimes, after sending an email, you might see a system message in your Mail List View with an SMTP error code. An SMTP error code is a message from your email provider that can help us understand why your email could not be sent. These codes are displayed by BlueMail to give you insights into the issue.
Common reasons for these errors include the need to re-authenticate your email account (simply update your password), temporary unavailability of your provider's server, among others.
Below is a list of common error codes and the reasons they occur.
Common Error Codes
- 421 – Service not available. The connection will be closed.
- 432 – A password transition is needed. This error is often related to an authentication issue.
- 447 – Your message timed out because the receiving server was busy. Try resending your message after some time.
- 450 – Command failed because the user’s mailbox is unavailable (e.g., locked). Try again later.
- 451 – Command aborted due to a server error. Not your fault.
- 452 – Command aborted due to insufficient system storage on the server.
- 454 – Authentication failed. You must authenticate before sending mail (try to update your password within BlueMail).
- 501 – Syntax error in command arguments.
- 503 – Bad sequence of commands encountered by the server.
- 504 – Command parameter not implemented.
- 511 – Bad email address. Check the recipient's email address for typos.
- 521 – Connection rejected. This domain doesn't accept mail or the server might be down.
- 523 – Size limit exceeded. Your email is too large to be processed by the recipient's server.
- 530 – Authentication required. Authenticate your email account before sending mail (try to update your password within BlueMail).
- 535 – Authentication failed. Authenticate your email account before sending mail (try to update your password within BlueMail).
- 550 – User’s mailbox is unavailable (e.g., not found, or rejected for policy reasons).
- 551 – Recipient not local to the server. The server gives a forwarding address to try.
- 552 – Action aborted due to exceeded storage allocation.
- 553 – Command aborted because the mailbox name is invalid.
- 554 – Rejection from the recipient domain. This means 'Not allowed'. The address in the "Sent From" or "Send To" headers appears to have insufficient submission rights, is invalid, or is not authorized with the authentication used. Please check the recipient address.