Lately I receiving Spamming Mails to my domain And I Get it In my Inbox not junk ( I think its stolen E-mail from trusted domain)

How to check that the zimbra spam assassin which I install it with the zimbra package work?

I would like to ask if there is any way to block certain Domain to send e-mails to my domain OR block certain e-mail address to send to my domain ??

Thanks in advance