There isn't a way to change the from address, however, there is no need to do that.
When someone clicks reply on the email sent by Tradify it picks up the User's email address and sends it to that person. So make sure that the email address specified under the Staff Member record for each User is correct. (go to Settings > Staff Members)
Since the mailing system is system driven, the mailing facility has to work this way. If Tradify were to supplant the From Email Address with the User's Email Address, Mail Servers would flag emails sent by Tradify as spam and block them.
Feel free to test the email reply process yourself by sending an email to another internal mail address you have and then click reply when you get it. The "To address" will be the User's Email Address who sent the email originally from within Tradify.