Sometimes it is desirable to catch unqualified hostnames (i.e. those that don't have a domain name) specified in sender or recipient addresses, for example when gatewaying between two networks, where one requires fully qualified domain names. On an Internet-UUCP relay, unqualifed hostnames should be mapped to the uucp domain by default. Other address modifications than these are questionable.
The /usr/lib/smail /qualify file tells smail which domain names to tack onto which hostnames. Entries in the qualify file consists of a hostname beginning in column one, followed by domain name. Lines containing a hash sign as its first non-white character are considered comments. Entries are searched in the order they appear in.
If no qualify file exists, no hostname qualification is performed at all.
A special hostname of * matches any hostnames, thus enabling you to map all hosts not mentioned before into a default domain. It should be used only as the last entry.
At the Virtual Brewery, all hosts have been set up to use fully qualified domain names in the sender's addresses. Unqualified recipient addresses are considered to be in the uucp domain, so only a single entry in the qualify file is needed.