user received alot of spam mail

[GV IT]

one of my user received alot of spam mails overnight.

some are classify as spam and was delivered to junk folder but some are not and was delivered as normal emails that goes to his inbox.

is there anything wrong with spam filters ?

can i block based on key words in subject title ?

how do i go about blocking such a large amounts of spam mails

[#2]

You can block messages based on keywords, but such blocks are very easy to bypass and almost useless - all it takes for the attacker is to change a single symbol in the message. Best block by IP range or domain, where possible.