Redmine

Hello,
I consider using redmine for a project that is partially
driven by email requests from external users.
Those requests should be processed by an internal team,
which should be able to reply to the requests.
The project management software should be completely
concealed for the external users, as if they had
a normal email communication with the internal team.
The users wont have access to the software.
Is this possible with redmine?

I have configured redmine to automatically generate
issues from emails but both options for the setting
"unknown_user" are unsatisfactory:
"accept" forgets the sender email address
and "create" sends registration details to external users.
Is it possible to suppress sending registration details
and replace with some message "your request will be processed within the next x hours"?

Is there any other solution?

Thank you!