What happens to messages stored on Gmail's servers?
Gmail offers enough storage to keep copies of messages you might need to search for later. By leaving mail on our servers, you can download it to other computers in the future.* If you really don't want your messages stored in Gmail, you can automatically delete them when they are accessed with POP. After thirty days, deleted messages are permanently removed from Gmail.
* All messages may be downloaded to another computer once; after downloading mail, it will not download again.