What can be a consequence of unauthorized access to an SMTP server?

Unauthorized access to an SMTP server can lead to the sending of spam or malicious emails, which is a serious consequence. When an attacker gains access to an SMTP server, they can use it to send out vast quantities of unsolicited emails, often promoting scams, phishing attempts, or malware. This not only affects the integrity and reputation of the email service but can also have broader consequences, including impacting recipient systems and users who may fall victim to these malicious attempts. Additionally, the presence of such activity can cause the server to be blacklisted by other email providers, which can severely hinder legitimate email communications.

The other options do not align with the implications of unauthorized access to an SMTP server. Enhanced email performance and improved security filtering are outcomes related to secure and well-managed systems, not a result of unauthorized access. Automatic disconnection from users might occur due to various security protocols but is not a direct consequence of the unauthorized access in itself.