Exim: forward sent emails to Gmail
I am currently using Gmail as an archive and webmail for my local email account. This works great for receiving email (I just setup an alias that points to a local account and Gmail account) but not so great for sending email. When I use Gmail's SMTP servers, it adds a Sender header of my gmail acount, which shows up when the email is viewed. This wouldn't be a big deal, but it seems unprofessional.
So, I would like to setup exim to forward sent emails to my Gmail account with a modified subject line. So that when I send an email from Thunderbird using my local account, Exim will automatically forward a copy to my gmail account.
It would be important to be able to modify the subject line so that I can setup a filter in Gmail to automatically apply a label and archive the received messages.
Also, I would prefer to be able to do this at a user level (i.e. with something like a forward file) rather than have to edit the main exim.conf file.