C# Developer | Visual Studio for an .exe app

we need a little program.
in a nutshell the user must be able to insert values ​​in the little program, the little program elaborates values ​​and exports them in a pdf and as a last step sends the pdf to an email address via an STMP connection.
while entering the values ​​in the window below, give the user the possibility to enter the recipient's email address.
in the program setup there should be the possibility to insert STMP data for sending emails and changing values.
Below is an explanation and an example file is attached.
{The need is to have an external program that generates a document (RTF,
DOC, PDF) and send it by email.
The program will be called from my ERP via runshell.
The idea is to create a document template (I can have different templates a
depending on the type of document I have to send. Eg Invoice and / or Note of
Credit) indicating the variables necessary for its compilation; the
values ​​of these variables are passed to the program in a TXT, or XML, file
, saved in a specific folder (Local or on the server).
The program must generate the document, attach it to the email and send it to the
customer.
The sender of the email should be a PEC address (I still have to
discuss the details with the customer), the recipients can be both PEC
than normal addresses.
All information needed by the external program for processing
(template file, TXT file with values, name to be assigned to the attachment,
recipient email address, email subject, email test .....)
could be stored in a TXT file created at runtime for each
document to be sent and saved in the appropriate folder.}