Use Case: Block access to the SMTP service to prevent a user from sending email through an offsite mail server.
Solution: Create a host address object with the IP address 10.64.173.20 called “OffsiteMail” and then create a firewall rule as follows:
From Zone
LAN
To Zone
WAN
Services
SMTP
Source Address
Any
Destination Address
OffsiteMail
Match Action
Deny