What are you doing SASI?...

Whats the trouble?
Yes, SMTP-Proxy blocks most of fake mails and some mails are passed/delivered. I can see a difference of passed mails, there are 5 kb large instead of alle blocked mails with 6kb. Maybe the mail with 5KB are "better" fake mails because the main body is "optimized" and the proxy doesnt recognize this.

SMTP-Proxy can not block 100% of all fake mails, but thats normal and okay! Its okay to configure the smtp-proxy with best practise (spam-tab) and use additional RBL-filters. for example we use additional rbl-lists:

ix.dnsbl.manitu.net
dnsbl-1.uceprotect.net
zen.spamhaus.org
b.barracudacentral.org
bl.spamcop.net
bl.score.senderscore.com
bl.spameatingmonkey.net
fresh.spameatingmonkey.net

and last spam blocker are the enduser, train them so they can recognize those fake mails.

Whats the trouble?
Yes, SMTP-Proxy blocks most of fake mails and some mails are passed/delivered. I can see a difference of passed mails, there are 5 kb large instead of alle blocked mails with 6kb. Maybe the mail with 5KB are "better" fake mails because the main body is "optimized" and the proxy doesnt recognize this.

SMTP-Proxy can not block 100% of all fake mails, but thats normal and okay! Its okay to configure the smtp-proxy with best practise (spam-tab) and use additional RBL-filters. for example we use additional rbl-lists:

ix.dnsbl.manitu.net
dnsbl-1.uceprotect.net
zen.spamhaus.org
b.barracudacentral.org
bl.spamcop.net
bl.score.senderscore.com
bl.spameatingmonkey.net
fresh.spameatingmonkey.net

and last spam blocker are the enduser, train them so they can recognize those fake mails.