This server is not joined to a domain, it's only trying to use ntlm_auth for the email module to send notifications.
My suspicion is that a regression was introduced when a CVE was closed off, judging by googling "unable to initialize messaging context"
I'm thinking some combination of syntax in the CEmailSenderModule + samba options + god knows what, is triggering the error, but is otherwise functional in both older and newer versions of samba. It looks like people have been running into this bug sporadically ever since the CVE was patched. ([PATCH] Fix bug 13465 (samba.org))
I inquired about possibly downgrading/upgrading the package in #centos and was informed;
So, i'm hoping that the updated package resolves the issue. I'll report back when i've updated.