Whenever Exim is called, it is passed options and arguments specifying what the caller wants it to do. Because you can call Exim from a shell in this way, this is called the command-line interface. In practice, most calls of Exim come directly from other programs such as MUAs, and do not involve an actual “command line.” However, the options and arguments are the same.
Many command-line options are compatible with Sendmail, so Exim can be a drop-in replacement, but there are additional options specific to Exim. Some options can be used only when Exim is called by a privileged user, and these are noted in what follows.
The command-line options are many, but they can be divided into a number of functional groups as follows:
Options to start processes for receiving incoming messages
Options to supply information to be incorporated into an incoming message that is submitted locally
Options to control whether a locally submitted message is delivered immediately on arrival, possibly depending on the type of recipient addresses
Options to control how errors in a locally submitted message are reported
Options for starting queue runners and selecting which messages they process
Options for overriding the normal configuration file
Options for inspecting messages on the queue
Options for forcing deliveries ...