Q:

How to add new 'From' email id each time sending email using PostFix server

I am new to PostFix and have setup PostFix as a server recently.  In the testing, PostFix is working fine and relaying the emails with 'From' email address stored in the PostFix credentials files likes admin@mydomain.com and password : xxxxxxx
My problem is: We have a web application that allows direct email sending feature between the website users.  As User 1 can send email to User 2 (user2@example.com) and vise verse.  But while sending emails using the PostFix server, the user2 will always receive the admin@mydomain.com instead of user1@example.com so the user2 can not reply on the email directly to the user1. 
This problem is a bigger one as we have thousands of the users that are waiting for this feature.  So if someone can help me configuring the PostFix server so that at the time of sending email, user can set their email id as the 'From' field of the email using any web form and the receiving user will get the email as the email was originally generated by user1@example.com so that he can reply directly to the user 1 on his email id.
I have done some research work on the PostFix about this problem but did not find much interesting one.  The approach others followed are using the smtp_generic_maps but this can work only with a limited set of email ids stored in the >>/etc/postfix/generic.  But we want this solution fully dynamic so that any user can add the FROM as his/her email while internally the email will be sent using the admin@mydomain.com in PostFix. 
Early response is much appreciated. 
Thanks

A:

Finally I fixed this issue by using an Grails application which doesn't require for adding fixed emails in the PostFix. 
Use the Grails Mail plugin and set PostFix server as the default Mail server. 
Also add inbound connection in the Postfix so that other email services will not ban you. 
As well as change the port from 25 to some other port as Port 25 is being used to send Trozen horses and spamming ..
I love PostFix now.. Enjoy free mail service for your small business. 
Thanks

