Have you tried https://blt.spamhaus.com/ ?
Also see my post here https://community.mailcow.email/d/1921-rspamd-rbls-configure-for-mailcow-differ-from-rspamd-defaults/4
There’s 2 places where the spamhaus look ups can work
1) postfix (postscreen)
2) rspamd
My understanding, the way mailcow configures itself is for #1 only. If you want it work at rspamd as well, follow the steps in my link above.
Check your data/conf/postfix/main.cf for presences of dqs.
Mine looks like this. This file is automatically generated and should not be edited directly. When you add your dqs key to mailcow.conf, shutdown/restart, it should update main.cf.
postscreen_dnsbl_sites = wl.mailspike.net=127.0.0.[18;19;20]*-2
hostkarma.junkemailfilter.com=127.0.0.1*-2
list.dnswl.org=127.0.[0..255].0*-2
list.dnswl.org=127.0.[0..255].1*-4
list.dnswl.org=127.0.[0..255].2*-6
list.dnswl.org=127.0.[0..255].3*-8
ix.dnsbl.manitu.net*2
bl.spamcop.net*2
bl.suomispam.net*2
hostkarma.junkemailfilter.com=127.0.0.2*3
hostkarma.junkemailfilter.com=127.0.0.4*2
hostkarma.junkemailfilter.com=127.0.1.2*1
backscatter.spameatingmonkey.net*2
bl.ipv6.spameatingmonkey.net*2
bl.spameatingmonkey.net*2
b.barracudacentral.org=127.0.0.2*7
bl.mailspike.net=127.0.0.2*5
bl.mailspike.net=127.0.0.[10;11;12]*4
dnsbl.sorbs.net=127.0.0.10*8
dnsbl.sorbs.net=127.0.0.5*6
dnsbl.sorbs.net=127.0.0.7*3
dnsbl.sorbs.net=127.0.0.8*2
dnsbl.sorbs.net=127.0.0.6*2
dnsbl.sorbs.net=127.0.0.9*2
SPAMHAUS_DQS_KEY.zen.dq.spamhaus.net=127.0.0.[4..7]*6
SPAMHAUS_DQS_KEY.zen.dq.spamhaus.net=127.0.0.[10;11]*8
SPAMHAUS_DQS_KEY.zen.dq.spamhaus.net=127.0.0.3*4
SPAMHAUS_DQS_KEY.zen.dq.spamhaus.net=127.0.0.2*3