To test if SpamAssassin is working properly, send an email to a user who is configured to receive spam-filtered email. Once the email has been received, examine the headers. There should be lines similar to the following:
X-Spam-Checker-Version: SpamAssassin 3.00 (2004-07-20) on mta.domain.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=4.0 tests=BAYES_00,DATE_IN_PAST_96_XX, NO_REAL_NAME,RCVD_IN_SORBS autolearn=no version=2.63
If headers like these are present, then SpamAssassin has run correctly. If the email is not received or the extra headers are not present, then SpamAssassin has failed to work.
Several tests can be performed to analyze the problem. Some were covered in Chapter 6 in Verifying the Installation ...