Postfix With SASL Authentication?

[Drew Tomlinson]

Can anyone point me to a HOW-TO to enable Postfix to relay for clients
that provide a valid login?  In other words, if I tell my IMAP client
that my outgoing SMTP server requires authentication and provide an
existing username/password combination that exists in /etc/passwd, I
want Postfix to relay the message even if the client isn't defined in
the "mynetworks" list.

I've searched Google and found that SASL should be able to do this so
I've installed it via the port.  I've also installed the saslauthd port
and recompiled Postfix with SASL support.  Now I think I want to
configure SASL to use PAM?  Anyway, I've found various tidbits on Google
and it seems that lots of people have problems with this.  Is there any
doc that helps one configure this on FBSD?

Thanks,

Drew