What's Causing This Error
SMTP error 535 indicates an issue with the client's authentication with the email server. It may be the result of many issues, some of the most common causes being:
- Invalid credentials.
- Disabled account.
- Invalid or incompatible connection encryption settings.
- Invalid or incompatible Authentication Methods.
Solution - Here's How To Resolve It
Depending on the cause of this error, the user may need to take different approaches when attempting to fix this error.
- The user must validate the credentials used to login into the email server.
- Check if the account is in working order and is not disabled.
- Validate the SMTP configuration to check if the connection encryption and authentication settings are compatible with the email server.