About once every 24 hours I get 4 to 7 emails from "john@somedomain.com" through my newsletter signup form. It's always "John", and the domains are random, valid domains. The "user" submits from a different ip every time.

My main question is - what's the point? Is this indicative some something else going on with my forms that isn't so apparent? I do filter the data so injection isn't possible... is there some other exploitation that may be going on?