Our server has slowed down over the past few months. We have Cacti monitoring processes on the server, and the threshold gets constantly triggered. I suspect that SPAM / Phishing messages are being sent to the server and either hitting non-valid email addresses and those messages are all scanned for SPAM/Viruses. AmavisD seems to eat alot of CPU during certain times.

I'm looking into how to improve the anti-spam.

What are the recommended smtpd_recipient_restrictions in /opt/zimbra/postfix/conf/main.cf

I currently have these settings:
smtpd_recipient_restrictions = reject_non_fqdn_recipient, permit_sasl_authenticated, permit_mynetworks, reject_unauth_destination, reject_unlisted_recipient, reject_non_fqdn_sender, permit

smtpd_reject_unlisted_recipient = no
Should that be changed to yes? What's effect will it have?

What are the benefits of these: