I have a kind of unvoluntary ping to my mailbox hosted at Gmail / Google Apps, "Buy Vigara" (sic) messages that arrive with a few minutes intervals since months

I have a kind of unvoluntary ping to my mailbox hosted at Gmail / Google Apps, "Buy Vigara" (sic) messages that arrive with a few minutes intervals since months ago. Google sorts them as spam correctly, but it is interesting to see how they are less and less frequent over the past hours. (Yes my domain is on godaddy)