Exim Transport and Delivery

Exim is a Mail Transport Agent written at Univeristy of Cambridge in England.

Mail addresses

Internet Mail Addresses
Exim insists that each e-mail address contain an "@" sign separating the local and domain parts. An address without an "@" sign is an "unqualified address" and Exim will automatically qualify it by appending @graphics.stanford.edu
Extension Addresses
For inbound mail, a userid, e.g. descartes, defines all local addresses of the form descartes-anything, as well as the address descartes itself. Delivery to descartes-anything is controlled by the file ~descartes/.exim-anything. For example, if a message comes to descartes-cs248, then Exim will look for delivery instructions in ~/.exim-cs248 If that file does not exist, exim will use the instructions in the ~/.exim file.
Warning: You can use these extension addresses to set up simple personal mailing lists. However, be aware that because of the above behavior, if you mistype an outbound message, e.g. to descartes-CS248, then it will still get delivered via ~/.exim and you will not see that it wasn't remailed via the extension address.

Mail delivery

When receiving mail for user descartes, Exim looks for delivery instructions in a file named ~descartes/.exim. If that files is missing or empty default delivery is made to /u/descartes/Mailbox. If the file has attributes which make it group or world-writable, Exim will not trust it and will hold messages until the file is made writable only by its owner.

Each line in a non-empty .exim file provides a single delivery instruction specifying either:

comment
Lines beginning with "#" are not processed
command pipeline
Lines beginning with "|" are pipelines run in a shell (/bin/sh) and are typically used in filtering mail.
file
Lines beginning with a "/" designate local files in either traditional mbox (if the line does not end in "/") or qmail's maildir format (if the line does end in "/"). The maildir can be a useful format but is not supported by our imap server.
Note: Exim does expand ~ so you must use /u/descartes
forwarding address
All other lines are processed as comma-separated lists of internet mail addresses as defined above.
They must by fully-qualified names and not contain any spaces, e.g. descartes@graphics.stanford.edu not descartes@graphics

An empty or missing .exim file for user descartes is equivalent to one containing:

/u/descartes/Maildir