stop spam with none <> as "from" header.

[ZaNaToS]

I see hunderds of spam using my server to be send and I cant stop them...
the characteristic is the from of the emails is " from <>" so they have no email as from..

If I run a simple check in my log files I see this:

root /scripts# tail -f /usr/local/psa/var/log/maillog | grep "from <>"
Jun 4 17:03:53 linux17 qmail: 1180969433.011027 info msg 10813749: bytes 13689 from <> qp 5167 uid 2522
Jun 4 17:03:56 linux17 qmail: 1180969436.775245 info msg 10813749: bytes 13689 from <> qp 5167 uid 2522
Jun 4 17:03:56 linux17 qmail: 1180969436.787230 info msg 10813749: bytes 13689 from <> qp 5167 uid 2522
Jun 4 17:03:57 linux17 qmail: 1180969437.498191 info msg 10813749: bytes 13689 from <> qp 5167 uid 2522
Jun 4 17:03:57 linux17 qmail: 1180969437.518096 info msg 10813749: bytes 13689 from <> qp 5167 uid 2522
Jun 4 17:03:58 linux17 qmail: 1180969438.049337 info msg 10813749: bytes 13689 from <> qp 5167 uid 2522
Jun 4 17:03:58 linux17 qmail: 1180969438.049871 info msg 10846320: bytes 3703738 from <> qp 10849 uid 2522
Jun 4 17:03:58 linux17 qmail: 1180969438.392554 info msg 10813749: bytes 13689 from <> qp 5167 uid 2522
Jun 4 17:03:58 linux17 qmail: 1180969438.392673 info msg 6212269: bytes 2100422 from <> qp 10856 uid 2020
Jun 4 17:03:58 linux17 qmail: 1180969438.404118 info msg 10813749: bytes 13689 from <> qp 5167 uid 2522
Jun 4 17:04:12 linux17 qmail: 1180969452.655179 info msg 10813749: bytes 13689 from <> qp 5167 uid 2522
Jun 4 17:04:12 linux17 qmail: 1180969452.710596 info msg 10813749: bytes 13689 from <> qp 5167 uid 2522
Jun 4 17:04:15 linux17 qmail: 1180969455.666100 info msg 10813749: bytes 13689 from <> qp 5167 uid 2522
Jun 4 17:04:15 linux17 qmail: 1180969455.683985 info msg 10813749: bytes 13689 from <> qp 5167 uid 2522
Jun 4 17:04:15 linux17 qmail: 1180969455.705733 info msg 10813749: bytes 13689 from <> qp 5167 uid 2522


Is there any way to stop these messages ?