Hi Greenmoon,
So far we've been using Write API for scripting the creation of new users from our CRM (I work for an educational institution, so we want it to be closed to just our students and tutors), and Google SSO for them to auth in via pre-provisioned GApps accounts. The Mandrill Emailer plugin appears to be geared towards achieving a post from email feature, but Mandrill is balking at the suggested URL from the NodeBB plugin (/admin/plugins/emailer-mandrill/emailer-mandrill/reply), seemingly due to permissions errors as the URL resolves itself to /login?local=1 in the Mandrill URL field.
I'm assuming it's a version issue, as the Mandrill plugin isn't available outside of Github. Unfortunately this is a required feature in my spec for a forum, based on student/tutor demand, so we may end up forced down the Discourse route.