Currently, roundup reads the contents of the 'Resent-from' header and uses it in preference of the 'From' header when finding out the creator for an issue/message.

This is good in situations where you don't want to create  users for all persons sending mail, but instead want the new issues to be created by a known person which bounces them into the system.

There's another use case, though - support trackers where all incoming mail should create a new user if needed. When mail are sent to other addresses, the best thing to do is to bounce it into the tracker, which should then set the original submitter as creator. This is currently not possible.

This behaviour should be configurable using the configuration file.

http://comments.gmane.org/gmane.comp.bug-tracking.roundup.user/7520 has a small discussion on this.