SMTP error 540 signals your email was rejected due to problems with the sender's email address or domain. This permanent error (5xx) indicates the recipient server can't deliver the message because of sender information issues. This can occur in applications like phpmailer and jenkins when sending emails.

What are the cases covered in SMTP Error 540?

Common scenarios triggering SMTP Error 540:

1. Nonexistent Sender: The provided "MAIL FROM" address or "From:" field in the email doesn't correspond to a valid sender account or is formatted incorrectly (phpmailer, jenkins).
2. Invalid Sender Domain: The sender's email domain (e.g., example.com) is non-existent, expired, or has DNS (Domain Name System) problems.
3. Unauthorized Sender: The recipient server requires specific authorization or credentials for emails from a particular domain or sender, and these are missing or invalid.

What’s Causing This SMTP Error 540 In Your Servers?

Potential causes of SMTP Error 540:

• Incorrect Sender Address: Double-check that the sender's email address is formatted accurately, spelled correctly, and belongs to a valid, authorized sender account (phpmailer, jenkins).
• Domain Issues: Verify that the sender's email domain is functioning properly, has no DNS issues, and isn't temporarily or permanently unavailable for sending emails.
• Contact Domain Administrators: If the sender's domain is experiencing problems, intervention from the administrators might be necessary to resolve technical issues or adjust email sending policies.

How to Resolve SMTP Error 540 - Step-by-Step Solution

1. Verify Sender Address: Ensure the sender's email address is formatted correctly, spelled accurately, and corresponds to a valid, authorized sender account (phpmailer, jenkins).
2. Check Sender Domain: Confirm that the sender's email domain is functioning properly, has no DNS issues, and isn't temporarily or permanently unavailable for sending emails.
3. Contact Domain Administrators: If the sender's domain is experiencing issues, it may require intervention from the administrators to resolve technical problems or adjust their email sending policies.

SMTP Error 540 Examples

• "540 5.1.1 sender@example.com: Sender address does not exist or is invalid."
• "540 5.4.5 sender@example.com: Sender's domain name not found. Check sender domain."
• "540 5.7.0 sender@example.com: Unauthorized sender. Email blocked due to policy reasons."

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