There is also an overview which expands on these features. Exim has an extensive set of documentation included in the exim specification, additionally there are documents on the filtering functionality and other documentation is being made available on this web site. The full overview is also available . Basic Features Many configuration options can be given as expansion strings, and as these can include file lookups, much of Exim's operation can be made table-driven if desired. For example, it is possible to do local delivery on a machine on which the users do not have accounts.
Regular expressions are available in a number of configuration parameters.
Domain lists can include file lookups, making it possible to support a large number of local domains. The maximum size of message can be specified. These are commonly called virtual domains . Exim contains an optional built-in mail filtering facility. This enables users to set up their own mail filtering in a straightforward manner without the need to run an external program.