Milter-greylist

> You mean it prefers unformatted man pages to the formatted ones?

yes 

> Anyone has a suggestion on how to decide when the unformatted man pages
> should not be installed? 

within SunOS the files under man/man? are typically of type nroff 

# file /usr/local/man/man8/mi* 
/usr/local/man/man8/mimedefang-multiplexor.8:   [nt]roff, tbl, or eqn input text
/usr/local/man/man8/mimedefang.8:       [nt]roff, tbl, or eqn input text
/usr/local/man/man8/mimedefang.pl.8:    [nt]roff, tbl, or eqn input text

and this brings a usable output:
nroff -man /usr/local/man/man8/mimedefang.8 

other os's have gnu-ziped man-pages, within redhat 
some of them are also of type nroff.
in this case man does the following:
gunzip -c /usr/share/man/man1/ls.1.gz | nroff -man 

but i did never care about the nroff/troff formating stuff.

best regards 
hans 

--