[Asked this on stackoverflow and was referred here]
We are developing a custom web app for a client. This app is on a separate server, server.com, than the client's web site, www.client.com. Each user of our app has an email address like firstname.lastname@example.org, email@example.com, etc. The client is using Google Apps for business for their user emails (like firstname.lastname@example.org).
Now here's what we need: Each user needs to be able to send certain emails to people on his contact list. Those emails are from our box, server.com. But we want the From and Reply-To address to be the user who sent it, e.g., email@example.com.
How can we set up our box, server.com, to be an authorized sender of emails from "client.com"? I looked up the SPF record for Google apps, and it is:
v=spf1 include:_spf.google.com ~all
(1) How do we add "server.com" to this SPF record?
(2) From PHP, how can we ensure that the email, while sent from our server.com, still says "From: firstname.lastname@example.org"?