Where to go from here

Documentation
exim: http://www.exim.org
exiscan-acl: http://duncanthrax.net/exiscan-acl/
spamassassin: http://www.spamassassin.org/
clamav: http://clamav.elektrapro.com/
spf: http://spf.pobox.com/

Support (mailing lists, forums)
exim-users: http://www.exim.org/maillist.html
exiscanusers: http://duncanthrax.net/exilist/exilist.cgi.pl
spamassassin: http://www.spamassassin.org/lists.html
clamav: http://clamav.elektrapro.com/ml.html
spf-discuss: http://spf.pobox.com/mailinglist.html