4.10 Using alias

4.10 Using ~alias

Although qmail automatically handles deliveries to most users with entries in the Unix password file (or qmail's adjusted version of it; see Chapter 15), any useful mail setup also needs to deliver mail to addresses unrelated to entries in the password file. Qmail handles this in a simple, elegant way with the alias pseudo-user. As part of the installation process, create a user called alias and set its home directory to /var/qmail/alias. When qmail is running, if mail arrives for a local mailbox that isn't in the normal list of users, qmail prepends alias- to the address and retries the delivery. This makes any address not otherwise handled in effect a subaddress of alias, so you can handle addresses by putting .qmail files into ~alias. For example, if you have a user robert and want mail addressed to bob to be forwarded to him, create ~alias/.qmail-bob and in it put &robert. Since qmail handles deliveries using the .qmail files in ~alias the same way that it handles any other deliveries, you have all of the same options delivering to nonuser addresses that you do to user addresses.

Because qmail doesn't deliver to root and other users that have a 0 user ID or that don't own their home directories, you should arrange to send root's mail to the system manager by creating ~alias/.qmail-root. Also create .qmail-postmaster, .qmail-abuse, .qmail-webmaster, and any other role addresses that you want to support.

The final default delivery is, not surprisingly, found in ~alias/.qmail-default. If that file doesn't exist, unknown addresses bounce, often just what you want. The most common thing to put in that file is a line to run the fastforward program (see the next section) to take delivery instructions from a file of addresses, roughly as sendmail does. You can also implement other default delivery rules. For example, if you want to make mail to subaddresses of ~alias users default to the base address, so mail to fred-foop is delivered to fred if it's not otherwise handled, put a line like this in your default delivery file. (It appears wrapped here, but it has to be on one long line in the file.)

| case "$DEFAULT" in *-*) forward "${DEFAULT%%-*}" ;; *) bouncesaying  "Sorry, no mailbox here by that name. (#5.1.1)" ;; esac

This says that if an address contains a hyphen, strip off the hyphen and everything after it and redeliver it. Otherwise bounce the message. The bouncesaying command lets you provide your own failure message, but a simple exit 100 would do the trick as well, telling qmail to bounce.