Hey friend,

The answer to this will be very relative. Mailgun is going to give you connection information. You can either develop your application to use that connection information from scratch, or you can look for existing libraries that assist with SMTP authentication for the language you have chosen to code in. Most likely some type of library already exists. Here is an example of one for Python:

https://docs.python.org/3/library/smtplib.html

Jarland