emmac6 on "How to block spammers from subscribing to my blog through email?"

I'm suddenly having lots of spammers subscribing to my blog through email. more than 15/day, and it is increasing.
1) is there a way of preventing this?
there does not seem any way of deleting them.
2) is my blog threatened?
3) also, I receive sometimes 4 emails telling me that a user has just subscribed, but 4 emails about that same user! - all spammers anyway
4) what's going on? why suddenly?
My blog is: http://wordsandpeace.com
Thanks for your help
Emma