Forum .LRN Q&A: sending notifications through smtp?

I have .LRN 2.3.1 installed on a debian etch box. I have set up an external SMTP server to be used in /etc/config.tcl, and when a new user is added, they receive an email with their account details, and I receive an email that a new user has been added. However, notifications don't seem to be working on .LRN. If I'm subscribed to a class' file folder, I don't receive a message when a file is uploaded. Similarly, when I use the community 'email members' page, the message is never sent out. Do I need to install a mail server in order to send those notifications out, or is there some way to send them out through SMTP?

Thanks,
Lacinda