postgrey 1.37-1 (s390x binary) in ubuntu kinetic

 This package provides a policy server for Postfix to implement "greylisting".
 .
 Greylisting is a spam filtering method that rejects email from external
 servers on the first try. Spammers don't usually retry sending their
 messages, whereas legitimate mail servers do.
 .
 While Postgrey is designed for use with Postfix, it can also be used
 with Exim.