There are some methods to consider:
1) Click the EMAIL SUPERVISOR icon as that allows you to message anyone and retains the history in the Incident. You can "Lookup" users or manually enter email addresses if they are not a current user.
2) If the Incident has a contact person, a "MailTo" link will be available to contact the person using your default email solution vs. the Dude Message Center. Note, this feature will not retain your email in the Incident's History.
3) When viewing a list of Incidents, you will notice a yellow envelope that defaults to messaging the contact person and default content to follow up with a user upon completion of work (can be overwritten). A list of Incident is accessible from any status next to the graph on the home page.
Options 1 and 3 above allow you to open the message center in a new window or tab in addition to retaining communication history.