2018-05-25 18:55:46.797 [9730] 1fMBwM-0002Rr-MX ** test@gmail.com F=<cpaneluser@host.abc.com> R=enforce_mail_permissions: Domain abc.com has an outgoing mail suspension. Message discarded.
Received that error and to lift the suspension ran the following command through ssh:
[root@host /]# whmapi1 unsuspend_outgoing_email user=cpaneluser
—
metadata:
command: unsuspend_outgoing_email
reason: OK
result: 1
version: 1
Could send properly again after that.