Error Description
SMTP error 540 is a permanent or "5xx" error code returned by a mail server to indicate that it has rejected an email message due to issues related to the sender's email address or domain. This error signifies that the email message cannot be delivered because of problems with the sender's information.
What's Causing This Error?
SMTP error 540 can be caused by several reasons, including:
- Non-existent sender: The sender's email address provided in the "MAIL FROM" command or the "From:" field of the email message does not correspond to a valid sender account or is not properly formatted.
- Invalid sender domain: The sender's email domain (e.g., example.com) does not exist, has expired, or has DNS (Domain Name System) issues.
- Sender not authorized: The recipient server may require specific authorization or credentials for sending emails from a particular domain or sender, and this authorization is lacking or invalid.
How to fix SMTP Error 540?
- Verify sender's email address: Ensure that the sender's email address is correctly formatted, is spelled correctly, and corresponds to a valid and authorized sender account.
- Check sender domain: Confirm that the sender's email domain is functioning correctly, does not have DNS issues, and is not temporarily or permanently unavailable for sending email.
- Contact sender domain administrators: If the sender's domain is experiencing issues, it may require intervention by the administrators to resolve technical problems or adjust their email sending policies.
SMTP Error 540 Examples
Example 1: "540 5.1.1 sender@example.com: Sender address does not exist or is invalid."
Example 2: "540 5.4.5 sender@example.com: Sender's domain name not found. Check sender domain."
Example 3: "540 5.7.0 sender@example.com: Unauthorized sender. Email blocked due to policy reasons."
