Hi CoyoteKG,
the first thing I noticed, were some common intruders, as you can see here:
Jun 29 20:54:55 africka-sljiva plesk_saslauthd[25670]: No such user '
[email protected]' in mail authorization database
Jun 29 20:54:55 africka-sljiva plesk_saslauthd[25670]: failed mail authenticatication...