Incoming E-Mail in OpenACS works with the latest version of acs-mail-lite in a general fashion using callbacks to interface with individual package features.
A scheduled like acs_mail_lite::inbound_queue_pull processes incoming email by loading each email and triggering callbacks.
Alternately, return email can be processed via notifications package. Forums package uses this method. See usage of notification::reply::get in forums/tcl/forum-reply-procs.tcl. notification::reply::get is defined in notifications/tcl/notification-reply-docs.tcl. To use this method, install the notifications package, and read documentation in notifications package.
Note: Notifications package requires ACS-Mail-Lite package. ACS-Mail-Lite is the most direct way of interfacing with email send and receive.
Please file bugs in the Bug Tracker.