ssmtp, gmail, and fEmail from address

It seems there's no way to set a custom from address? Every email sent always shows the one configured in /etc/ssmtp for the AuthUser line.

$email = new fEmail;
$email->setFromEmail($from_email);
$email->setReplyToEmail($from_email);
$email->setSenderEmail($from_email);
$email->setSubject($subject);
$email->addRecipient($user->getEmailAddress());
$email->setBody($body);
$email->send();

Having no luck whatsoever. I guess Gmail is very strict? I would think the Reply-To header would at least be allowed.