Please consider the following approach:
In case your Movelet originates from an integrated scenario, e.g. into SAP Netweaver, you could consider sending the user input to your back-end system via a reply or data container.
In the back-end system you could use all the power you have to apply formatting, mail templates, enrich or convert the content (PDF report) and then use build in functions to finally distribute the content to the recipients. Additionally the back-end could store a reference of the mail conversation, to keep track of the exchange.
In SAP ABAP there are mechanisms for that, same applies for all other sophisticated programming languages, I assume.
Hope this helps,
Tom!
Appendix:
In SAP you could evaluate class CL_BCS (Business Communication Service), but there are many more options for this.