Hi there,
I'm having some trouble getting my contact form to send emails in production mode. My code is largely unchanged from the Contact controller from the WidgiCorp sample site that was included in the 0.9.1 release.
Running on my localhost, I had originally set $config['dev_mode'] = TRUE in MY_config.php and all was working fine. But to simulate what it would be like when the site's running in my remote hosting environment, I've set 'dev_mode' to FALSE and added my SMTP info to the $config array (protocol, smtp_host, smtp_user, smtp_pass) in /application/config/email.php. This causes it to fail.
UPDATE: I've figured it out: the From address must be owned by the originating SMTP server. If you're asking for a user's email address, then set that with reply_to() instead.