This patch is a variant of the qmailscannerdomains patch.

By default, qmail-scanner scans incoming mail for every recipient. However, in
some environments - especially commercial installations, where only paying
customers should be able to use qmail-scanner - it is desirable to enable it
per domain.

While the qmailscannerdomains patch controlled the use of the whole 
qmail-scanner functionality, some people desired to have virus scanning for all 
domains, while only providing SpamAssassin checks for paying customers.

This patch invents a new control file, /var/qmail/control/spamassassindomains.
If this file doesn't exist, qmail-scanner works as normal. If it exists, it
should contain recipient domains to scan mails for, one domain per line.
qmail-scanner still scans every mail for viruses, but SpamAssassin is only 
activated for domains listed there.

You can use both the qmailscannerdomains and this one together; but beware that 
the SpamAssassin scan is a subset of qmail-scanner functionality, so putting a 
domain into spamassassindomains, but not into qmailscannerdomains has no effect. 
You can check for viruses but not for spam, but you can't check for spam but not 
for viruses.

If you used the qmailscannerdomains patch and want to switch over to this one, 
but already have software that manages entries in qmailscannerdomains, just 
symlink that file to spamassassindomains.