[Dovecot] Dovecot SASL doesn't seem to be working with Postfix

[Jeremy Gillick]

If I setup the virtual users in Dovecot and enable SASL in Postfix, does
that mean that Postfix should use Dovecot for authentication and for the
virtual user table?  Is there anything I need to do outside the following to
instruction URLs to make this work?

http://wiki.dovecot.org/HowTo/SimpleVirtualInstall
http://wiki.dovecot.org/HowTo/PostfixAndDovecotSASL

I'm reading the ADDRESS_CLASS_README, but it seems like I'll have to mirror
the settings from Dovecot to Postfix.  That doesn't seem right:
http://www.postfix.org/ADDRESS_CLASS_README.html

Thanks,
Jeremy