`filter.d/exim.conf` - introduces mode `more` (several rules moved from mode `normal` to `more`), because:

- they have basically nothing with authentication;
- they can cause false positives (e. g. someone sends several mails from google mailing server to wrong recipients and if they would cause "rejected RCPT - Unknown user", the google host gets banned;
- to avoid occasional ban of legitimate servers one'd need create large white-list for `ignoreip` or construct complex `ignorecommands` to exclude all legitimate servers of big players (like google, microsoft, GMX, etc);

config/filter.d/exim.conf

@@ -15,17 +15,19 @@ before = exim-common.conf
 
 prefregex = ^%(__prefix_line)s<F-CONTENT>.+</F-CONTENT>$
 
-failregex = ^%(host_info)s sender verify fail for <\S+>: (?:Unknown user|Unrouteable address|all relevant MX records point to non-existent hosts)\s*$
-            ^\s?\w+ authenticator failed for%(host_info)s: 535 Incorrect authentication data(?: \(set_id=.*\)|: \d+ Time\(s\))?\s*$
-            ^%(host_info)s rejected RCPT [^@]+@\S+: (?:relay not permitted|Sender verify failed|Unknown user|Unrouteable address)\s*$
+failregex = ^\s?\w+ authenticator failed for%(host_info)s: 535 Incorrect authentication data(?: \(set_id=.*\)|: \d+ Time\(s\))?\s*$
+            <mdre-<mode>>
+
+mdre-more = ^%(host_info)s sender verify fail for <\S+>: (?:Unknown user|Unrouteable address|all relevant MX records point to non-existent hosts)\s*$
+            ^%(host_info)s rejected RCPT (?:<F-RCPT>[^@]+@\S+:</F-RCPT>)?
             ^\s?SMTP protocol synchronization error \([^)]*\): rejected (?:connection from|"\S+")%(host_info)s (?:next )?input=".*"\s*$
             ^\s?SMTP call from%(host_info)s dropped: too many (?:(?:nonmail|unrecognized) commands|syntax or protocol errors)
             ^\s?SMTP protocol error in "[^"]+(?:"+[^"]*(?="))*?"%(host_info)s [A-Z]+ (?:command used when not advertised|authentication mechanism not supported)\s*$
             ^\s?no MAIL in SMTP connection from%(host_info)s
             ^\s?(?:[\w\-]+ )?SMTP connection from%(host_info)s closed by DROP in ACL\s*$
-            <mdre-<mode>>
 
-mdre-aggressive = ^\s?no host name found for IP address <ADDR>$
+mdre-aggressive = %(mdre-more)s
+                  ^\s?no host name found for IP address <ADDR>$
                   ^\s?no IP address found for host \S+ \(during SMTP connection from%(host_info)s\)$
                   ^%(host_info)s dropped by '[^']+' ACL: