PureMessage contains thousands of spam tests that analyze individual characteristics of each message. Each of these tests has a numerical weight. When a message is analyzed by PureMessage, the weights from all the spam tests that matched the message are added up and converted to a spam score that expresses the message's "spam probability".
By default, PureMessage checks for spam in messages that originate from outside the network, but it can also be configured to test messages originating within the local domain. If a message is found to have a spam probability of 50% or more, it is copied to the PureMessage quarantine. By default, PureMessage also delivers these messages, but alters the message's subject heading to show its spam probability.
PureMessage handles incoming email as follows: