1 Answer

Block a Sender in Gmail

To have Gmail send messages from a specific sender to the Trash automatically:

Click the Show search options triangle in the Gmail search field.
Type the desired email address under From:.
You can block an entire domain by entering just that. To block all mail from both user-a@example.com and user-b@example.com, type "@example.com".
To block more than one address, separate them with "|" (the vertical bar; typically above the backslash on the keyboard; not including the quotation marks). You can block both user-a@example.com and user-b@example.com by typing "user-a@example.com|user-b@example.com", for example.
Click Create filter with this search ».
Make sure Delete it is checked under When a message arrives that matches this search:.
Click Create filter.
Check Also apply filter to __ matching conversations to delete previously received messages. 

http://email.about.com/od/gmailtips/qt/et_block_sender.htm