"G-mail" has a very good spam blocker, and at times ... they're wrong. But very easy to fix at your end. When you're looking at your e-mail main page (on the left) is a column listing number of unread e-mails, spam that's been stopped, etc.
Check the 'spam' one out (Dear God there are a lot of folks who want to sell you 'male enhancement products!
)) See one that's not spam, click on it, then click the 'not spam' button. This will transfer it to your regular 'in-box' and the sender won't be blocked again. At least the above works for me.