Needed: How to use own Mail Server for Contact Forms

While testing the contact form and the tutorial on the "hire-me" page we found out that a javascript is used to send the message. Is it correct that the data is sent to the recipient via a script which is located on bootstrapstudio? How can I use my own mail server so that I don't have to rely on Javascript? Of course a tutorial would be great.

with regards, Kay from Germany