We have a typical business web app that allows our users to send e-mails with offerings to their clients. We set user e-mail in FROM field so the client can reply directly t
Exactly which routine are you using to send the Email? We send emails via raw SMTP using HTTP put_lines and the replies bounce back to the address we nominate in the FROM: field.
See if your SMTP API wrapper has a Reply To: field
Some APIs might not provide that functionality because it increases the possibility of spamming.