Spam

Why does zoho seem to have their good months and bad months when it comes to spam? I've been using zoho for a while now and I've noticed that when spam filtering doesn't work it just fails to learn and continually lets spam through. I've been instructed in the past to move spam into the spam folder and leave it to allow the system to learn new spam but this one specific piece of spam from ' ViagrCial@xxxx.com' always comes through. The domains are random so blacklisting them is next to impossible but even when the body of the message is over 95% identical each time the system still doesn't recognize it as spam even after weeks of receiving emails anywhere from five to twenty five times a day! It's getting quite annoying, is there any plans of a user submission option to help teach the system or perhaps a new filter or filter options being applied in place of the current system?