Reason for being non-free: djb license. no distribution of modified versions. no binary distribution.
Replacements: courier-mta, postfix, exim4
Debian Lenny to be shipped with qmail and djbdns in main In 2007, Dan J. Bernstein decided to change the licence terms for his software, therefore, qmail and djbdns may be distributed in Debian main with the next stable release.