White list

A white list, as opposed to a black list, is a list of accepted people/companies/elements/anything.

If an organization keeps a white list of software, only titles on the list will be accepted for use (A school might white list MATLAB and Netscape Navigator)

If a spam filter keeps a white list, only mail from the listed addresses will be allowed.

"Whitelist" can also be used as a verb, meaning to put on a white list.