From 'mail log', no information sending mail (sendmail or stmp) from your server but many spammer try to brute-force for smtp. Fortunely, always failed.
Different between Kloxo-MR 6.5 and 7.0, in 7.0 also try to reject/block brute-force for smtp (beside for ssh and ftp). In your case, Kloxo-MR 7.0 possible to reject/block IP 210.3.184.74.