[Dovecot] can't receive mail from other hosts

i'm running RHEL v 5 and 1.0-1.2.rc15 of dovecot and 2.3.3-2 of postfix. users can send mail to outside hosts, but can not receive them. i find no errors in the maillog -- i used a page from the redhat docs to configure postfix and dovecot so that they used the same mail directory... i think...

any ideas on how to debug and/or fix this would be greatly appreciated.

thanks, steve