Exchange user send mail error 421 4.3.2 sent 10 spam today, such email sending will be limited

Hello

 my exchange server 2019  show in queue this mesage : " 421 4.3.2  xxx.yyy.zzz.qqq sent 10 spam today, such email sending will be limited "  despite that the anti-spam is not installed   any idea about this message ???

thanks

Thanks