I've set up sendmail to just send out mails from our php web application. That works fine, as long as we are not sending mail to the same domain as our web app.
our app = www.ourapp.com sending mails works perfectely, except for firstname.lastname@example.org"
I don't know if it's relevant, but our target email is hosted with google apps. Sendmail queue is empty and the log files always say the message has been sent
we are running CentOS as our OS