Here’s my recommended SpamAssassin settings:

To turn away spam at the front door:

In Exim Configuration Manager check “No bouncing by spam score” and set the SpamAssassin “reject score threshold” to something reasonable, eg 8.

To rank spam your way, override the /etc/mail/spamassassin/local.cf defaults. Eg:

score MICROSOFT_EXECUTABLE 20.0
score RCVD_IN_BRBL_LASTEXT 5.5
score RCVD_IN_BL_SPAMCOP_NET 5.5
score RCVD_IN_SBL 5.5
score RCVD_IN_XBL 5.5
score RCVD_IN_PBL 5.5
score RCVD_IN_DSBL 5.0
score RCVD_IN_SORBS_HTTP 3.5
score RCVD_IN_SORBS_MISC 3.5
score RCVD_IN_SORBS_SMTP 4.5
score RCVD_IN_SORBS_SOCKS 3.5
score RCVD_IN_SORBS_WEB 3.5
score RCVD_IN_SORBS_BLOCK 4.5
score RCVD_IN_SORBS_ZOMBIE 3.5
score RCVD_IN_SORBS_DUL 4.5
score HTML_TAG_BALANCE_BODY 2.0
score HTML_TAG_BALANCE_HEAD 3.0
score HTML_IMAGE_ONLY_04 4.0
score HTML_MESSAGE 0.3
score INVALID_DATE 3.2
score RCVD_IN_NJABL_SPAM 3.5
score RCVD_IN_NJABL_PROXY 5.5
score RCVD_IN_NJABL_RELAY 4.5
score RCVD_IN_NJABL_MULTI 2.5
score RCVD_IN_NJABL_CGI 2.5
score ONLINE_PHARMACY 7.0
score SUBJ_YOUR_FAMILY 7.0
score URIBL_SBL 7.0
score URIBL_SC_SURBL 7.0
score URIBL_WS_SURBL 7.0
score URIBL_PH_SURBL 7.0
score URIBL_OB_SURBL 7.0
score URIBL_AB_SURBL 7.0
score URIBL_JP_SURBL 7.0
score URIBL_BLACK 7.0
score URIBL_DBL_SPAM 7.0
score RCVD_ILLEGAL_IP 5.0
score RATWARE_RCVD_PF 5.0
score RDNS_NONE 5.0
score RAZOR2_CHECK 3.0
score URIBL_RHS_DOB 3.8
score BAYES_99 9.5
score BAYES_95 8.0
score BAYES_80 7.0
score BAYES_60 5.0
score BAYES_50 4.5
score BAYES_40 2.0
score BAYES_00 -1.5
score DIET_1 0.5
score RP_MATCHES_RCVD -0.1
score CANT_SEE_AD 5.0