Can you rewrite the "Return-Path:" header

[PUMPY2]

I am trying to integrate Exchange 5.5 with Clearswift Mailsweeper for SMTP 4.3

A problem exists where our Exchange users who only have permissions to send external email on behalf of an inbox linked to a public folder in Exchange server try to send this mail externally. Exchange sets the internet headers for mail sent by J.Bloggs@company.com on behalf of Department@company com as follows

Return-path: <J.Bloggs@company.com>
From: "Department" <Department@company.com>

The Clearswift Mailsweeper software authenticates the value set in "Return-Path" and not in "From:" I cannot set the address J.Bloggs@company.com up in Mailsweeper as an authenticated user as this will permit them to route external email from their own address as well as the departmental address. Is it possible to either force the "Return-Path:" header to always match the "From:" header or alternatively is it possible within Exchange to prevent individuals from routing external email from their own address but allow then to route external email from a departmental email address linked to a public folder