Some doubts about gmail.....

i have a gmail account. And i have the following questions,

1) And i accidentally gave adress to one of the company who uses to send 4 or 5 mails a day. Now how can i do atomatic deletion of that messages.

2) How to delete all messages at once. I am having 2k mails in inbox and it will be a pain to delete 100 by 100.

thanks.