"Intercept" actions prevent a message from being delivered to the mailbox of the original recipient. Instead, the message is deleted, quarantined, or sent to a different recipient.
"Intercept" actions are "terminal" actions. Once a terminal action executes, processing of that rule stops and no further action takes place for that rule.
Terminal actions execute following a strict priority order:
Delete the entire message.
Deliver the message now.
The Deliver now action is not recommended for use as the only action. If you choose Deliver now as the only action for Spam mail, for example, all of that mail will simply be delivered to your recipients, as if there were no spam filter in place.
If you use Deliver now with a virus rule, ensure that you also have a Delete action for the virus rule. Only the Delete action takes higher priority than Deliver now and so would be processed before it (and then terminate the processing of that rule).
If you chose Deliver now as the only action for a virus rule, mail containing viruses would leak through unblocked.
Quarantine the message.