Security Features

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qmail includes the following security features:

• Compartmentalization of delivery targets. There is a clear distinction between addresses, files, and programs that prevents attackers from writing to security-critical files and executing arbitrary programs with elevated privileges.

• Minimization of setuid() code. Only one module, qmail-queue, runs setuid().

• Minimization of root code. Only two modules runs as root: qmail-start and qmail-lspawn.

• Five-way trust partitioning. Five qmail-specific user IDs are used to partition trust within the qmail system. A compromise to the system should be contained to one partition.

• Logging. Using the QUEUE_EXTRA compile-time option, logging of one-way message hashes, entire message contents, or other desired information is possible for all messages or subsets of messages (for example, messages from or to a specified user or domain).

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