The PureMessage system does not have a facility for identifying "safe senders." If you need to receive e-mail that is currently marked as "spam?###" you should set your spam threshold low (the default) or choose to mark-and-deliver all e-mail (like the old system), or you can opt-out of the service completely (not recommended). Most email clients, including Outlook, allow for the creation of a safe or trusted senders list. This is also called a "white list."
The PureMessage system does not have a facility for individuals to block specific senders. You night want to keep your spam threshold low or opt-out of the service completely and use your email client filtering capabilities to block specific senders.
For specific information on how to set up filters for your email client see How to Filter and Setup Rules for Email Messages.