Limit SMTP or disable Pop/SMTP access for some users

Hi,
In Zimbra, we could create CoS and specify which user would be able to access POP/SMTP etc and which would not. In that way, we would be able to limit our POP/SMTP usage, which is safe in case someone’s computer gets compromised.
But in Carbonio CE, we do not have that freedom anymore. Now can anyone please suggest how I can limit the following scenarios?

1. I do not want certain users to use POP/SMTP, they must use webmail.
2. I want to limit 5 outgoing mails per user, so that they cannot flood the system in case their computer is compromised.

Would appreciate if you can suggest me how to do that.