X-Authentication-Warning (FreeBSD 8.1 STABLE)

[Andy Wodfer]

Hi,
A client is sending out a newsletter and I'm trying to set the FreeBSD
server user (www) to be trusted so that I don't get this warning in the
message header:

X-Authentication-Warning: host.domain.net: www set sender to
post at domain.netusing -f

I assume this is to be set in the sendmail.cf file (Twww), but on my FreeBSD
8.1 STABLE I have both a sendmail.cf and a freebsd.cf aswell as a
freebsd.submit.cf. I haven't played around with sendmail for a couple of
years, but I also seem to remember that you don't just edit the .cf file,
but infact edit the mc file and compile, install and restart?

Can someone please guide me through here?

PS! I'm the only login user on this system, but are there security issues
related to this that I should be concerned with?

Thanks!
Andy