If you're using Mail as your mail program, the messages are stored in home/Library/Mail.
Under 10.7, the ~/Library folder is hidden. However, you can get there by holding down the Option key and clicking the Go menu in the Finder. You'll see Library as an option in that menu. Once you're there, you can enter Time Machine in the usual way to view your backups.
Thanks for your suggestion but Unfortunately, I have had a problem with Mail, therefore, I have been using safari pop acct to access my email. I visited an Apple Store and the folks there said they would have not problem disabling my pop server and setting Mail, however, they were quite sure that all me emails would be deleted. They suggested backing up my computer with the time machine. they said that since all my emails were stored in my computer that they would be included in the backup. I have backed up my computer, but can't find the backed up emails.
While Mail is running, enter Time Machine.
Your old e-mail account should reappear.
Restore that e-mail account and all the messages should come with it.
Once you have the account back, you can create a folder "On your Mac" for them and move all the messages into that folder. Then you can re-delete the account.