Create a file in: /etc/mail/spamassassin
Call it anything you like, for eg: rules.cf
Paste these rules as is within it which should stop alot of spam:
score URIBL_SBL 5.0
score URIBL_AB_SURBL 5.0
score URIBL_OB_SURBL 5.0
score URIBL_PH_SURBL 5.0
score URIBL_SC_SURBL 5.0
score URIBL_WS_SURBL 5.0
score URIBL_JP_SURBL 5.0### Custom Score Ratings
score AXB_XMAILER_MIMEOLE_OL_4379D 2.6score RAZOR2_CHECK 1.9
#score RAZOR2_CHECK 0
#score RAZOR2_CF_RANGE_E8_51_100 0# SPF-related scores
score SPF_PASS -2.05
score SPF_NEUTRAL -0.201
score SPF_FAIL 1.75
score SPF_SOFTFAIL 1.5
score SPF_HELO_PASS -2.05
score SPF_HELO_FAIL 1.75
score SPF_HELO_SOFTFAIL 1.5score RCVD_NUMERIC_HELO 0.5
score FH_FROMEML_NOTLD 3.696#score BAYES_00 -2.5138
#score BAYES_05 -2.0138
#score BAYES_20 -1.5138
#score BAYES_40 -0.5138
#score BAYES_50 0.5138
#score BAYES_60 2.500
#score BAYES_70 2.750
#score BAYES_80 3.500
#score BAYES_90 4.000
#score BAYES_95 4.500
#score BAYES_99 5.005# score RCVD_IN_DSBL 0
score RCVD_IN_SBL 3.5
score RCVD_IN_PBL 3.5
score RCVD_IN_XBL 4.5
score RCVD_IN_BL_SPAMCOP_NET 2.5score BODY_8BITS 1.90
score HTML_FONT_FACE_BAD 1.50meta META_HELO_DYNAMIC_IP ((FH_HELO_EQ_D_D_D_D + HELO_DYNAMIC_IPADDR + MISSING_DATE) >1)
score META_HELO_DYNAMIC_IP 1.500#score URI_HEX 2.453
#score URI_HEX 4.921score URIBL_SBL 2.468
score URIBL_SC_SURBL 2.523
score URIBL_WS_SURBL 2.101
score URIBL_PH_SURBL 2.0235
score URIBL_OB_SURBL 2.132
score URIBL_AB_SURBL 2.101
score URIBL_JP_SURBL 2.857
score URIBL_BLACK 3.899
score URIBL_GREY 1.186
score URIBL_RED 0.005#score RCVD_IN_SORBS_WEB 1.619
score RCVD_IN_SORBS_DUL 0.05score FH_HOST_EQ_PACBELL_D 2.673
#score RCVD_IN_BONDEDSENDER -5
#score HABEAS_SWE 0score NO_DNS_FOR_FROM 5.501
score HELO_NO_DOMAIN 0.001
score SUBJ_ALL_CAPS 1.00
score SUBJ_ILLEGAL_CHARS 4.516
score SUBJECT_FUZZY_MEDS 1.98
score SUBJECT_NEEDS_ENCODING 1.823
score HTML_MIME_NO_HTML_TAG 0.968
#score MIME_HTML_ONLY 1.825
score HTML_MESSAGE 0.107
score MISSING_SUBJECT 1.000score MIME_QP_LONG_LINE 1.094
#score DCC_CHECK 2.654
score DCC_CHECK 1.184
#score PYZOR_CHECK 2.701#toned down from 3.116 because spamd might not recognize a new version of outlook
score FORGED_MUA_OUTLOOK 2.516### http://home.comcast.net/~mkettler/sa/antidrug.cf
score DRUGS_ERECTILE 4.681
score DRUGS_ERECTILE_OBFU 4.301
score DRUGS_DIET 2.01
score DRUGS_DIET_OBFU 3.0
score DRUGS_PAIN 2.01
score DRUGS_PAIN_OBFU 3.0
score DRUGS_SLEEP 2.01
score DRUGS_MUSCLE 2.01
score DRUGS_ANXIETY 2.01
score DRUGS_ANXIETY_OBFU 3.0
score DRUGS_DEPRESSION 2.01
score DRUGS_SMEAR1 3.5
score DRUGS_DIET_EREC 3.0
score DRUGS_PAIN_EREC 3.0
score DRUGS_DEPR_EREC 3.0
score DRUGS_ANXIETY_EREC 3.0
score DRUGS_DIET_PAIN 2.5
score DRUGS_SLEEP_EREC 2.5
score DRUGS_MANYKINDS 3.0score MALE_ENHANCE 3.996
score KAM_LOTTO1 3.004
score KAM_LOTTO2 4.009score RCVD_IN_DOB 3.007
score DNS_FROM_DOB 3.009#score UPPERCASE_50_75 1.423
#score UPPERCASE_75_100 1.528score DEAR_WINNER 4.197
score DNS_FROM_RFC_DSN 2.527
score DNS_FROM_RFC_BOGUSMX 2.325#score TVD_PH_SUBJ_URGENT 2.797
score DATE_IN_FUTURE_03_06 2.303
score DATE_IN_FUTURE_06_12 3.099
score DATE_IN_FUTURE_12_24 3.300
score DATE_IN_FUTURE_24_48 3.599
score DATE_IN_FUTURE_48_96 3.199
score DATE_IN_FUTURE_96_XX 3.899score DATE_IN_FUTURE_03_06 2.303
score DATE_IN_FUTURE_06_12 3.099
score DATE_IN_FUTURE_12_24 3.300
score DATE_IN_FUTURE_24_48 3.599
score DATE_IN_FUTURE_48_96 3.199
score DATE_IN_FUTURE_96_XX 3.899score FH_HELO_ALMOST_IP 0.001
score HELO_DYNAMIC_IPADDR 0.001
score HELO_DYNAMIC_IPADDR2 0.001
score HELO_DYNAMIC_DHCP 0.001
score HELO_DYNAMIC_HCC 0.001score RCVD_IN_PBL 0.300
score DOS_OE_TO_MX_IMAGE 0.500
score DOS_OE_TO_MX 0.500score HELO_DYNAMIC_SPLIT_IP 0.001
score NORMAL_HTTP_TO_IP 0.384
score PART_CID_STOCK 1.0
score DC_GIF_UNO_LARGO 0.152
score FAKE_REPLY_C 1.102score FRT_PRICE 2.475
score RCVD_IN_DNSWL_NONE 0
score RCVD_IN_DNSWL_LOW 0
score RCVD_IN_DNSWL_MED 0
score RCVD_IN_DNSWL_HI 0score RCVD_IN_BRBL_LASTEXT 3.6
score RDNS_NONE 0.9
Also download KAM Rules – http://www.pccc.com/downloads/SpamAssassin/contrib/KAM.cf