What does SMTP authentication help prevent?

SMTP authentication helps prevent unauthorized access to send emails through the server by requiring senders to verify their identity before allowing them to use the email server for sending messages. This process typically involves the sender providing a valid username and password. By ensuring that only authenticated users can send emails, SMTP authentication protects the server from being exploited by spammers or malicious users who might attempt to send unsolicited or harmful messages, thus maintaining the integrity and reputation of the email service.

The other options, while related to email management, do not directly connect to the primary purpose of SMTP authentication. For example, while it is possible for incorrect credentials to cause delivery failures, the main focus of SMTP authentication is on ensuring that only authorized users can send emails. Similarly, email delivery delays are generally associated with network issues or server overload rather than authentication processes. Access to spam filters is unrelated to the authentication process itself; instead, it pertains more to the rules and policies governing how incoming and outgoing emails are handled by the server.