smail is able to handle alias files compatible with those known by Berkeley's sendmail. Entries in the alias file may have the form
recipients is a comma-separated list of addresses that will be substituted for the alias. The recipient list may be continued across newlines if the next line begins with a TAB.
There is a special feature that allows smail to handle mailing lists from the alias file: if you specify ``:include:filename'' as recipient, smail will read the file specified, and substitute its contents as a list of recipients.
The main aliases file is /usr/lib/aliases. If you choose to make this file world-writable, smail wil not deliver any messages to shell commands given in this file. A sample file is shown below:
If an error occurs while delivering to an address generated from the aliases file, smail will attempt to send a copy of the error message to the ``alias owner''. For example, if delivery to biff fails when delivering a message to the development mailing list, a copy of the error message will be mailed to the sender, as well as to postmaster and owner-development. If the owner address does not exist, no additional error message will be generated.
When delivering to files or when invoking programs given in the aliases file, smail will become the nobody user to avoid any security hassles. Especially when delivering to files, this can be a real nuisance. In the file given above, for instance, the log files must be owned and writable by nobody, or delivery to them will fail.