Any system that is accessible through the Internet is subject to attempts to infiltrate the operating system's security or to exploit security weaknesses of services running on the system. Administrators should be concerned not only about these kinds of blatant attacks but also inadvertent actions by users. Some of the most serious breaches in security are caused by users who release sensitive data or cause a flood of mail from the Internet.
If you are using the Internet Mail Connector, you should consider how you will minimize the security risks when connecting Microsoft Exchange Server to the Internet. You can configure Microsoft Exchange Server and Windows NT Server to ensure that people in your organization can send and receive Internet mail but unauthorized users can't access your system from the Internet. You can also set up other mechanisms such as firewalls that protect against attacks.