Hello Sir,
I have seen the specification document and shall be able to develop this Addin within 3 days. As a better proposition, we can also first write the email then select contacts (from new button in top Ribbon) to insert info and send email. Please share which Outlook version do you need this for. As I am the highest rated Outlook Addin developer here, you may take a look at client's feedback on my past projects.
There is no need to make any advance payment. I am ready to accept full payment after the Add-in is developed and tested.
Thank you,
Usman