SMTP 530 Authentication Required vs 535 Authentication Failed
Both SMTP 530 (Authentication Required) and 535 (Authentication Failed) belong to the 5xx Permanent Negative category. 530 indicates that the server requires authentication before accepting mail commands. You must issue the AUTH command with valid credentials before attempting to send mail. Meanwhile, 535 means that the authentication credentials provided are invalid. The username, password, or authentication mechanism was rejected by the server.
Description
The server requires authentication before accepting mail commands. You must issue the AUTH command with valid credentials before attempting to send mail.
When You See It
When trying to send mail through a server that requires authentication (typical for submission on port 587) without first logging in with the AUTH command.
How to Fix
Authenticate using the AUTH command with your username and password before sending MAIL FROM. Ensure your email client is configured with the correct SMTP credentials and authentication method.
Description
The authentication credentials provided are invalid. The username, password, or authentication mechanism was rejected by the server.
When You See It
After submitting incorrect credentials via the AUTH command. The username or password does not match any account on the server.
How to Fix
Double-check your username and password. If using an app password (e.g., Gmail, Outlook), ensure it is current and has not been revoked. Also verify the correct SASL mechanism (PLAIN, LOGIN, etc.).
Key Differences
SMTP 530: The server requires authentication before accepting mail commands. You must issue the AUTH command with valid credentials before attempting to send mail.
SMTP 535: The authentication credentials provided are invalid. The username, password, or authentication mechanism was rejected by the server.
You encounter 530 when when trying to send mail through a server that requires authentication (typical for submission on port 587) without first logging in with the AUTH command.
You encounter 535 when after submitting incorrect credentials via the AUTH command. The username or password does not match any account on the server.
When to Use Which
For 530 (Authentication Required): Authenticate using the AUTH command with your username and password before sending MAIL FROM. Ensure your email client is configured with the correct SMTP credentials and authentication method. For 535 (Authentication Failed): Double-check your username and password. If using an app password (e.g., Gmail, Outlook), ensure it is current and has not been revoked. Also verify the correct SASL mechanism (PLAIN, LOGIN, etc.).