How can I customize the mail FROM header in our Email Marketing Application , to enable our customers to specify their OWN email ( from their domain ) . Currently the customer specify his own domain and we use it at the Reply-To mail's header. CURRENTLY From: [email protected] Reply-To: customer_email@customer_domain.com Return-Path: [email protected] WHAT WE NEED From: customer_email@customer_domain.com Reply-To: customer_email@customer_domain.com Return-Path: [email protected] We do it this way to avoid getting blacklisted because Mail Servers like Gmail or Hotmail would considers it as a MAIL'S HEADER FORGERY ATTEMPT. But our customers keeps asking us to make the FROM HEADER customizable. Can someone help us ?