Hello,
I've been working with MsOffice in the last few years, and the REST or the .Net API seems to be the obvious choice here. My final bid might vary depending on other requirements (like GUI integration or bulk sending), but feel free to contact me with further details.
In my work, I aim to add value to the project wherever I could, continuously keeping the customer up to date, while providing high quality and bug-free output.
Thank you for considering my application,
Stephen