White list

A white list (or to whitelist, the action), 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). This may be beneficial in that whitelisted software will be ensured to work perfectly, but can cause problems as other software which is known to work may be entirely unsupported by that organization.

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