This error occurs during the SMTP (Simple Mail Transfer Protocol) authentication process when a mail server or client attempts to authenticate using the LOGIN method but provides incorrect authentication data, such as a wrong username or password. It typically arises when sending emails through a server that requires authentication, signalling a mismatch between the provided credentials and the server’s expectations.
Error Message
Failed to authenticate on SMTP server with username "abc@gmail.com" using 2 possible authenticators. Authenticator LOGIN returned Expected response code 235 but got code "535", with message "535 Incorrect authentication data". Authenticator PLAIN returned Expected response code 235 but got code "535", with message "535 Incorrect authentication data"Follow these step-by-step instructions to fix the issue:
- Login into WHM.
- Go to ‘Server Configuration’.
- Click on ‘Tweak Settings’.
- Go to the ‘Mail Tab’.
- Search for Restrict outgoing SMTP to root, exim, and mailman (FKA SMTP Tweak).
- Change the default on to off
- Save the new setting
