Error Description

SMTP error 535 is a permanent or "5xx" error code returned by a mail server to indicate that it has rejected an email message due to authentication failure. This error signifies that the sender's email client or server failed to provide valid or acceptable credentials when attempting to send the email.

What's Causing This Error?

SMTP error 535 can be caused by several reasons, including:

• Incorrect or incomplete login credentials: The sender's email client or server provided incorrect or incomplete username and password when attempting to authenticate with the recipient server.
• Failed authentication mechanism: The recipient server may require specific authentication methods (e.g., SMTP-AUTH) that were not used or configured incorrectly by the sender.
• Suspended or restricted account: The sender's email account with the recipient server may be suspended, locked, or restricted from sending email, making authentication impossible.

How to fix SMTP Error 535?

• Verify authentication credentials: Ensure that the username and password provided for SMTP authentication are correct, complete, and correspond to a valid sender account.
• Configure authentication correctly: If the recipient server requires specific authentication methods, configure your email client or server to use the appropriate mechanisms, such as SMTP-AUTH.
• Address account issues: If your email account is suspended, locked, or restricted, contact the email administrator or hosting provider to resolve the account-related issues.

SMTP Error 535 Examples

Example 1: "535 5.7.0 Authentication failed. Please check your username and password."

Example 2: "535 5.7.1 Incorrect authentication mechanism. Use SMTP-AUTH for secure login."

Example 3: "535 5.5.0 Account locked. Email sending is temporarily restricted."