when an update is received to an issue via email the status is set to the designated "feedback received" status
3 parts:

1. under administration | issue statuses | there is a check box for "feedback received" status.
2. when an email is received to an issue where the status is changed to the designated "feedback received" status. this would only happen for emails at this point. someone using the form would of course be able to change the status on their own.

The advantage of this is that you can see what issues are updated via email where they cannot change the status.

Environment:
Redmine version 2.4.1.stable
Ruby version 1.8.7-p352 (2011-06-30) [x86_64-linux]
Rails version 3.2.16
Environment production
Database adapter PostgreSQL
SCM:
Subversion 1.6.17
Git 1.7.9.5
Filesystem

Redmine plugins:
no plugin installed