Jim Kinter - 2018-07-27

I just setup someone with a Usermin acct to be able to use the readmail/webmail feature only.
Incoming mail works just fine, but their outgoing mail never got to the recipient (tested sending to myself).

/var/log/maillog shows (sensitive information CHANGED) :

from=USEREMAIL@DOMAIN.com, size=558, class=0, nrcpts=1, msgid=1532704772.30975@DOMAIN.com, relay=USER@localhost
to=ME@DOMAIN.com, ctladdr=USEREMAIL@DOMAIN.com (532/509), delay=00:00:01, xdelay=00:00:01, mailer=relay, pri=30558, relay=[127.0.0.1] [127.0.0.1], dsn=5.0.0, stat=Service unavailable
DSN: Service unavailable

So I tried logging in as ME and sending to one of my emails (all emails are on this same server), and got the same error (to test that it wasnt the new user acct).
I have been running this sendmail server for years using 3rd party client software without any issues.
If I email manually from cmdline, it goes through just fine, so it appears to be something 'not quite right' in usermin config.

I remember a few years ago I had a client using usermin webmail without problem, so curious if something changed in an update somewhere.

Feels like I am missing an obscure checkbox somewhere.....
Google isnt being of much help.
Any help would be appreciated

CentOS Linux 7.1.1503
Linux mailsvr.MYCOMPANY.com 3.10.0-229.14.1.el7.x86_64 #1 SMP Tue Sep 15 15:05:51 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
Sendmail version 8.14.7
Webmin ver 1.890
Usermin ver 1.680