Sending email but not receiving

[vuecare]

I've got Sentora installed on CentOS 7, and am able to send email, but not receive.
I find the following error in /var/dovecot.log when I try to send an email to an account hosted by Sentora:

Fatal: setuid(xyz from userdb lookup) failed with euid=994(vmail):
Operation not permitted (This binary should probably be called with process user set to xyz instead of 994(vmail)

I am also still getting a warning that the server does not support TLS when I us mxtoolbox, but I presume that is an unrelated issue.