I have a mail server all set up and running on ubuntu 14.04 with Postfix / Dovecot for the domain "postfixserver.com".
A second domain "googleapps.com" is running on google apps.
firstname.lastname@example.org emails are forwarded from google apps to email@example.com.
When firstname.lastname@example.org replies to an email addressed to email@example.com I would like postfix to send the email out as being from firstname.lastname@example.org.
Is there any way to achieve this without having to rely on the email client. So for instance on an iPhone I would like to only setup one account email@example.com but being able to reply to emails sent to firstname.lastname@example.org keeping the correct from address.