I apologize if my question is stupid.:
Does somebody know if the plesk qmail has HELO/EHLO checking?
For example, spam can be greatly reduced by a number of simple checks confirming compliance with standard addressing and MTA operation.
In many situations, simply requiring a valid FQDN in the SMTP EHLO statement is enough to block 25% of incoming spam.
* Refusing connections from hosts that begin transmission prior to presentation of the receiving host's HELO banner
* Refusing connections from hosts that give an invalid HELO - for example, a HELO that is not an FQDN or is an IP address not surrounded by square brackets.................