Okay everyone... I've spent the past month really fine-tuning the SpamAssassin rules (especially after SpamAssassin was upgraded to 4.0 with Cloudron 8.3), and it seems to be working quite well for me. Spam filtering is never perfect, but it has improved a lot since the last time I took a look at the rules. The list is much longer now, and I added many more rules along with some additional lists for extra checks too.
If you want to use Abusix (which I've found to be very reliable), then you'll need a free API key, and can replace <API_KEY> in the list below with your own.
As always, your own mileage may vary, but this should be an effective SpamAssassin rule set to use. Good luck. 
# ============================
# Allowlist / Blocklist Rules
# ============================
score USER_IN_BLOCKLIST 50.0
score USER_IN_ALL_SPAM_TO -50.0
score USER_IN_MORE_SPAM_TO -10.0
score USER_IN_WELCOMELIST -50.0
## Block specific recipients/senders
blocklist_from <EMAIL>
## Allowlist specific recipients/senders
welcomelist_from <EMAIL>
# ============================
# Bayesian Filtering (BAYES)
# ============================
bayes_auto_learn 1
bayes_auto_learn_threshold_nonspam -4.0
bayes_auto_learn_threshold_spam 12.0
score BAYES_00 -6.0
score BAYES_05 -4.0
score BAYES_20 1.5
score BAYES_40 2.5
score BAYES_50 3.25
score BAYES_60 3.75
score BAYES_80 4.25
score BAYES_95 5.5
score BAYES_99 7.0
score BAYES_999 7.5
# ============================
# DNS-based Blocklists (DNSBL)
# ============================
## DNS Blocklists
score RCVD_IN_BL_SPAMCOP_NET 2.5
score RCVD_IN_MSPIKE_BL 0.0
score RCVD_IN_MSPIKE_L2 1.0
score RCVD_IN_MSPIKE_L3 1.5
score RCVD_IN_MSPIKE_L4 3.5
score RCVD_IN_MSPIKE_L5 5.0
score RCVD_IN_MSPIKE_ZBI 4.0
score RCVD_IN_PBL 3.5
score RCVD_IN_SBL 5.0
score RCVD_IN_SBL_CSS 4.0
score RCVD_IN_VALIDITY_RPBL 1.5
score RCVD_IN_XBL 6.0
score RCVD_IN_ZEN_BLOCKED 0.0
score RCVD_IN_ZEN_BLOCKED_OPENDNS 0.0
## DNS Whitelists
score RCVD_IN_DNSWL_BLOCKED 0.0
score RCVD_IN_DNSWL_HI -6.0
score RCVD_IN_DNSWL_LOW -2.5
score RCVD_IN_DNSWL_MED -4.5
score RCVD_IN_DNSWL_NONE 0.0
score RCVD_IN_MSPIKE_H2 -1.0
score RCVD_IN_MSPIKE_H3 -1.5
score RCVD_IN_MSPIKE_H4 -3.5
score RCVD_IN_MSPIKE_H5 -5.0
score RCVD_IN_MSPIKE_WL 0.0
# ============================
# URI Blocklists (URIBL)
# ============================
score URIBL_ABUSE_SURBL 6.0
score URIBL_BLACK 7.0
score URIBL_CR_SURBL 3.5
score URIBL_CSS 3.0
score URIBL_CSS_A 3.0
score URIBL_DBL_ABUSE_BOTCC 5.5
score URIBL_DBL_ABUSE_MALW 5.5
score URIBL_DBL_ABUSE_PHISH 5.5
score URIBL_DBL_ABUSE_REDIR 2.0
score URIBL_DBL_ABUSE_SPAM 5.5
score URIBL_DBL_BLOCKED 0.0
score URIBL_DBL_BLOCKED_OPENDNS 0.0
score URIBL_DBL_BOTNETCC 5.5
score URIBL_DBL_ERROR 0.0
score URIBL_DBL_MALWARE 5.5
score URIBL_DBL_PHISH 5.5
score URIBL_DBL_SPAM 5.5
score URIBL_GREY 0.5
score URIBL_MW_SURBL 5.0
score URIBL_PH_SURBL 5.0
score URIBL_RED 2.0
score URIBL_RHS_DOB 2.0
score URIBL_SBL 4.0
score URIBL_SBL_A 3.0
score URIBL_ZEN_BLOCKED 0.0
score URIBL_ZEN_BLOCKED_OPENDNS 0.0
# ============================
# Email Authentication (SPF/DKIM/ARC)
# ============================
## DKIM
score DKIM_INVALID 2.0
score DKIM_ADSP_ALL 2.0
score DKIM_ADSP_CUSTOM_MED 1.5
score DKIM_ADSP_NXDOMAIN 4.5
score DKIM_SIGNED 0.0
score DKIM_VALID 0.0
score DKIM_VALID_AU 0.0
score DKIM_VALID_EF 0.0
score DKIM_VERIFIED 0.0
score DKIMWL_BL 3.0
score DKIMWL_WL_HIGH -6.0
score DKIMWL_WL_MED -4.0
score DKIMWL_WL_MEDHI -4.5
score USER_IN_DEF_DKIM_WL -6.0
## SPF
score FORGED_SPF_HELO 4.0
score SPF_FAIL 4.0
score SPF_HELO_FAIL 2.5
score SPF_HELO_NEUTRAL 1.0
score SPF_HELO_NONE 0.25
score SPF_HELO_PASS -1.0
score SPF_HELO_SOFTFAIL 4.0
score SPF_NEUTRAL 0.0
score SPF_NONE 1.0
score SPF_PASS -1.0
score SPF_SOFTFAIL 1.5
score T_SPF_PERMERROR 2.0
score T_SPF_TEMPERROR 0.0
score USER_IN_DEF_SPF_WL -6.0
## ARC
score ARC_INVALID 2.0
score ARC_SIGNED 0.0
score ARC_VALID -0.5
# ============================
# HTML & MIME Structure Rules
# ============================
score HTML_FONT_LOW_CONTRAST 0.0
score HTML_FONT_SIZE_LARGE 2.0
score HTML_FONT_TINY_NORDNS 0.0
score HTML_IMAGE_ONLY_04 1.25
score HTML_IMAGE_ONLY_08 1.25
score HTML_IMAGE_ONLY_12 1.25
score HTML_IMAGE_ONLY_16 1.25
score HTML_IMAGE_ONLY_20 1.25
score HTML_IMAGE_ONLY_24 1.25
score HTML_IMAGE_ONLY_28 1.25
score HTML_IMAGE_ONLY_32 1.25
score HTML_MESSAGE 0.0
score HTML_MIME_NO_HTML_TAG 0.5
score HTML_OBFUSCATE_05_10 0.5
score HTML_OBFUSCATE_10_20 1.0
score HTML_OBFUSCATE_20_30 2.0
score HTML_OBFUSCATE_30_40 2.5
score HTML_OBFUSCATE_50_60 3.0
score HTML_OBFUSCATE_70_80 3.5
score HTML_OBFUSCATE_90_100 4.0
score HTML_SHORT_LINK_IMG_1 2.0
score HTML_SHORT_LINK_IMG_2 3.0
score HTML_SHORT_LINK_IMG_3 3.0
score MIME_HTML_MOSTLY 0.0
score MIME_HTML_ONLY 0.0
score MPART_ALT_DIFF 0.5
score MPART_ALT_DIFF_COUNT 0.5
# ============================
# Header / Envelope Heuristics
# ============================
score HEADER_FROM_DIFFERENT_DOMAINS 2.0
score MISSING_DATE 2.5
score MISSING_FROM 2.0
score MISSING_HEADERS 2.5
score MISSING_MID 1.0
score MISSING_SUBJECT 1.0
score MSGID_OUTLOOK_INVALID 4.0
score MISSING_HB_SEP 2.0
score TO_NO_BRKTS_FROM_MSSP 1.5
score REPLYTO_WITHOUT_TO_CC 2.5
# ============================
# Freemail & Identity Rules
# ============================
score FREEMAIL_ENVFROM_END_DIGIT 1.0
score FREEMAIL_FORGED_REPLYTO 2.25
score FREEMAIL_FROM 0.0
score FREEMAIL_REPLY 0.5
score FREEMAIL_REPLYTO 2.0
score FREEMAIL_REPLYTO_END_DIGIT 0.0
score FROM_LOCAL_DIGITS 1.75
score FROM_EXCESS_BASE64 2.5
score FROM_FMBLA_NEWDOM 2.5
score FROM_FMBLA_NEWDOM14 3.0
score FROM_FMBLA_NEWDOM28 2.5
score FROM_SUSPICIOUS_NTLD 2.0
score FORGED_GMAIL_RCVD 3.0
score FORGED_MUA_OUTLOOK 3.0
score FORGED_YAHOO_RCVD 3.0
# ============================
# Scam, Phishing & Social Engineering
# ============================
score ADVANCE_FEE_2 3.0
score ADVANCE_FEE_2_NEW_MONEY 3.0
score ADVANCE_FEE_2_NEW_FORM 3.0
score ADVANCE_FEE_3 3.0
score ADVANCE_FEE_3_NEW 3.0
score ADVANCE_FEE_3_NEW_MONEY 3.0
score ADVANCE_FEE_3_NEW_FORM 3.0
score ADVANCE_FEE_4_NEW 3.0
score ADVANCE_FEE_5_NEW 3.0
score ADVANCE_FEE_5_NEW_FRM_MNY 3.0
score ADVANCE_FEE_5_NEW_MONEY 3.0
score BILLION_DOLLARS 1.0
score DEAR_FRIEND 1.5
score LOTS_OF_MONEY 0.0
score UNCLAIMED_MONEY 4.0
score URG_BIZ 1.5
score FUZZY_CLICK_HERE 1.5
score FUZZY_CREDIT 2.0
score FUZZY_IMPORTANT 2.0
score FUZZY_SECURITY 2.25
score FUZZY_UNSUBSCRIBE 1.0
score SUBJ_AS_SEEN 0.75
score SUBJ_DOLLARS 0.25
score SUBJ_YOUR_DEBT 2.5
score SUBJ_YOUR_FAMILY 0.75
# ============================
# Transport / Network Reputation Rules
# ============================
score NO_RDNS_DOTCOM_HELO 3.0
score RDNS_DYNAMIC 3.5
score RDNS_LOCALHOST 3.5
score RDNS_NONE 2.25
score RCVD_HELO_IP_MISMATCH 1.75
score RCVD_ILLEGAL_IP 4.0
score PDS_BAD_THREAD_QP_64 1.5
score TBIRD_SUSP_MIME_BDRY 2.5
score SPAMMY_XMAILER 2.75
score KHOP_HELO_FCRDNS -0.5
score HELO_DYNAMIC_IPADDR 2.0
score HELO_DYNAMIC_SPLIT_IP 2.0
score UNPARSEABLE_RELAY 0.0
# ============================
# URI & Link Obfuscation
# ============================
score URI_HEX 2.5
score URI_NO_WWW_BIZ_CGI 2.5
score URI_NO_WWW_INFO_CGI 2.5
score URI_OBFU_WWW 3.0
score URI_TRUNCATED 2.5
score HTTPS_HTTP_MISMATCH 0.25
score WEIRD_PORT 4.5
# ============================
# Miscellaneous Heuristics & Content Triggers
# ============================
score ENV_AND_HDR_SPF_MATCH -4.0
score DATE_IN_FUTURE_06_12 2.25
score DATE_IN_PAST_03_06 2.25
score DATE_IN_PAST_06_12 2.25
score PLING_QUERY 1.0
score SHOPIFY_IMG_NOT_RCVD_SFY 0.75
score T_FILL_THIS_FORM_SHORT 0.25
score T_REMOTE_IMAGE 0.25
score STOX_REPLY_TYPE 2.0
score STOX_REPLY_TYPE_WITHOUT_QUOTES 3.0
score SUSPICIOUS_RECIPS 2.5
# ============================
# Spam Eating Monkey DNSBL lists
# ============================
header RCVD_IN_SEM_BACKSCATTER eval:check_rbl('sembackscatter-lastexternal', 'backscatter.spameatingmonkey.net')
describe RCVD_IN_SEM_BACKSCATTER Received from an IP listed by Spam Eating Monkey Backscatter list
tflags RCVD_IN_SEM_BACKSCATTER net
score RCVD_IN_SEM_BACKSCATTER 3.0
header RCVD_IN_SEM_BLACK eval:check_rbl('semblack-lastexternal', 'bl.spameatingmonkey.net')
tflags RCVD_IN_SEM_BLACK net
describe RCVD_IN_SEM_BLACK Received from an IP listed by Spam Eating Monkey Blocklist
score RCVD_IN_SEM_BLACK 3.0
header RCVD_IN_SEM_NETBLACK eval:check_rbl('semnetblack-lastexternal', 'netbl.spameatingmonkey.net')
tflags RCVD_IN_SEM_NETBLACK net
describe RCVD_IN_SEM_NETBLACK Received from an IP listed by Spam Eating Monkeys Network Blocklist
score RCVD_IN_SEM_NETBLACK 1.5
urirhssub SEM_FRESH30 fresh30.spameatingmonkey.net. A 2
body SEM_FRESH30 eval:check_uridnsbl('SEM_FRESH30')
describe SEM_FRESH30 Contains a domain registered less than 30 days ago
tflags SEM_FRESH30 net
score SEM_FRESH30 3.0
urirhssub SEM_URI_BLACK uribl.spameatingmonkey.net. A 2
body SEM_URI_BLACK eval:check_uridnsbl('SEM_URI')
describe SEM_URI_BLACK Contains a URI listed by Spam Eating Monkeys URI Blocklist
tflags SEM_URI_BLACK net
score SEM_URI_BLACK 3.5
# ============================
# JunkEmailFilter HostKarma DNSBL & DNSWL
# ============================
header __RCVD_IN_HOSTKARMA eval:check_rbl('hostkarma', 'hostkarma.junkemailfilter.com.')
describe __RCVD_IN_HOSTKARMA Sender listed in JunkEmailFilter
tflags __RCVD_IN_HOSTKARMA net
header RCVD_IN_HOSTKARMA_W eval:check_rbl_sub('hostkarma','127.0.0.1')
describe RCVD_IN_HOSTKARMA_W Sender listed in HOSTKARMA-WHITE
tflags RCVD_IN_HOSTKARMA_W net nice
score RCVD_IN_HOSTKARMA_W -3.5
header RCVD_IN_HOSTKARMA_BL eval:check_rbl_sub('hostkarma','127.0.0.2')
describe RCVD_IN_HOSTKARMA_BL Sender listed in HOSTKARMA-BLACK
tflags RCVD_IN_HOSTKARMA_BL net
score RCVD_IN_HOSTKARMA_BL 3.0
header RCVD_IN_HOSTKARMA_BR eval:check_rbl_sub('hostkarma','127.0.0.4')
describe RCVD_IN_HOSTKARMA_BR Sender listed in HOSTKARMA-BROWN
tflags RCVD_IN_HOSTKARMA_BR net
score RCVD_IN_HOSTKARMA_BR 1.25
# ============================
# SpamRATS DNSBL
# ============================
header __RCVD_IN_SPAMRATS eval:check_rbl('spamrats', 'all.spamrats.com.')
describe __RCVD_IN_SPAMRATS SPAMRATS: sender is listed in SpamRATS
tflags __RCVD_IN_SPAMRATS net
reuse __RCVD_IN_SPAMRATS
header RCVD_IN_SPAMRATS_DYNA eval:check_rbl_sub('spamrats','127.0.0.36')
describe RCVD_IN_SPAMRATS_DYNA RATS-Dyna: sent directly from dynamic IP address
tflags RCVD_IN_SPAMRATS_DYNA net
reuse RCVD_IN_SPAMRATS_DYNA
score RCVD_IN_SPAMRATS_DYNA 2.25
header RCVD_IN_SPAMRATS_NOPTR eval:check_rbl_sub('spamrats','127.0.0.37')
describe RCVD_IN_SPAMRATS_NOPTR RATS-NoPtr: sender has no reverse DNS
tflags RCVD_IN_SPAMRATS_NOPTR net
reuse RCVD_IN_SPAMRATS_NOPTR
score RCVD_IN_SPAMRATS_NOPTR 2.5
header RCVD_IN_SPAMRATS_SPAM eval:check_rbl_sub('spamrats','127.0.0.38')
describe RCVD_IN_SPAMRATS_SPAM RATS-Spam: sender is a spam source
tflags RCVD_IN_SPAMRATS_SPAM net
reuse RCVD_IN_SPAMRATS_SPAM
score RCVD_IN_SPAMRATS_SPAM 5.5
# ============================
# UCEPROTECT
# ============================
header RCVD_IN_UCEPROTECT_LEVEL_1 eval:check_rbl('uceprotect1', 'dnsbl-1.uceprotect.net.')
describe RCVD_IN_UCEPROTECT_LEVEL_1 Sender IP listed in UCEPROTECT Level 1
tflags RCVD_IN_UCEPROTECT_LEVEL_1 net
score RCVD_IN_UCEPROTECT_LEVEL_1 4.0
header RCVD_IN_UCEPROTECT_LEVEL_2 eval:check_rbl('uceprotect2', 'dnsbl-2.uceprotect.net.')
describe RCVD_IN_UCEPROTECT_LEVEL_2 Sender IP listed in UCEPROTECT Level 2
tflags RCVD_IN_UCEPROTECT_LEVEL_2 net
score RCVD_IN_UCEPROTECT_LEVEL_2 1.25
# ============================
# Abusix Guardian Mail Relay
# ============================
header __RCVD_IN_ABUSIX eval:check_rbl('abusix', '<API_KEY>.combined.mail.abusix.zone.')
describe __RCVD_IN_ABUSIX Received via a relay in Abusix Guardian Mail
tflags __RCVD_IN_ABUSIX net
header RCVD_IN_ABUSIX_BLACK eval:check_rbl_sub('abusix', '^127\.0\.0\.(?:[23]|200)$')
describe RCVD_IN_ABUSIX_BLACK Received via a relay in Abusix Guardian Mail Black
tflags RCVD_IN_ABUSIX_BLACK net
score RCVD_IN_ABUSIX_BLACK 5.5
header RCVD_IN_ABUSIX_EXPLOIT eval:check_rbl_sub('abusix', '127.0.0.4')
describe RCVD_IN_ABUSIX_EXPLOIT Received via a relay in Abusix Guardian Mail Exploit
tflags RCVD_IN_ABUSIX_EXPLOIT net
score RCVD_IN_ABUSIX_EXPLOIT 6.0
header RCVD_IN_ABUSIX_DYN eval:check_rbl('abusix_dyn', '<API_KEY>.combined.mail.abusix.zone.', '^127\.0\.0\.1[12]$')
describe RCVD_IN_ABUSIX_DYN Received via a relay in Abusix Guardian Mail Dynamic
tflags RCVD_IN_ABUSIX_DYN net
score RCVD_IN_ABUSIX_DYN 1.5
header RCVD_IN_ABUSIX_WHITE eval:check_rbl('abusix_white', '<API_KEY>.combined.mail.abusix.zone.', '127.0.2.1')
describe RCVD_IN_ABUSIX_WHITE Received via a relay in Abusix Guardian Mail White
tflags RCVD_IN_ABUSIX_WHITE nice net
score RCVD_IN_ABUSIX_WHITE -1.5
urirhsbl URIBL_ABUSIX_DBLACK <API_KEY>.dblack.mail.abusix.zone. A
body URIBL_ABUSIX_DBLACK eval:check_uridnsbl('URIBL_ABUSIX_DBLACK')
describe URIBL_ABUSIX_DBLACK Contains a spam URL listed in the Abusix domain blocklist
tflags URIBL_ABUSIX_DBLACK net
score URIBL_ABUSIX_DBLACK 6.0
urirhssub URIBL_ABUSIX_WHITE <API_KEY>.white.mail.abusix.zone. A 127.0.2.1
body URIBL_ABUSIX_WHITE eval:check_uridnsbl('URIBL_ABUSIX_WHITE')
describe URIBL_ABUSIX_WHITE Contains a domain listed in the Abusix domain whitelist
tflags URIBL_ABUSIX_WHITE nice net
score URIBL_ABUSIX_WHITE -0.25
# ============================
# Ascams RBLs (IP Reputation)
# ============================
header RCVD_IN_ASCAMS_BLOCK eval:check_rbl('ascams_block', 'block.ascams.com.')
describe RCVD_IN_ASCAMS_BLOCK Sender listed in Ascams Block RBL
tflags RCVD_IN_ASCAMS_BLOCK net
score RCVD_IN_ASCAMS_BLOCK 1.25
header RCVD_IN_ASCAMS_DROP eval:check_rbl('ascams_white', 'dnsbl.ascams.com.')
describe RCVD_IN_ASCAMS_DROP Sender listed in Ascams DROP list
tflags RCVD_IN_ASCAMS_DROP nice net
score RCVD_IN_ASCAMS_DROP 3.0
# ============================
# DroneBL DNSBL
# ============================
header RCVD_IN_DRONEBL eval:check_rbl('dronebl', 'dnsbl.dronebl.org.')
describe RCVD_IN_DRONEBL Sender listed in DroneBL (suspected bot/malware)
tflags RCVD_IN_DRONEBL net
score RCVD_IN_DRONEBL 3.0
# ============================
# GBUDB Truncate DNSBL
# ============================
header RCVD_IN_GBUDB_TRUNCATE eval:check_rbl('gbudb', 'truncate.gbudb.net.')
describe RCVD_IN_GBUDB_TRUNCATE Sender listed in GBUDB Truncate
tflags RCVD_IN_GBUDB_TRUNCATE net
score RCVD_IN_GBUDB_TRUNCATE 4.0
# ============================
# Usenix S5H
# ============================
header RCVD_IN_S5H_BL eval:check_rbl_txt('s5hbl', 'all.s5h.net.')
describe RCVD_IN_S5H_BL Listed at all.s5h.net
tflags RCVD_IN_S5H_BL net
score RCVD_IN_S5H_BL 0.5
# ============================
# Backscatterer.org
# ============================
header RCVD_IN_BACKSCATTERER eval:check_rbl('backscatterer', 'ips.backscatterer.org.')
describe RCVD_IN_BACKSCATTERER IP listed in Backscatterer (backscatter spam)
tflags RCVD_IN_BACKSCATTERER net
score RCVD_IN_BACKSCATTERER 3.5
but I still don't see that out even as a beta release. Is there any ETA for when that will arrive by any chance?
