how do i see archived email when i offline?

what my intention
when I connected with internet then i can open all email. but some time when i  am not connected with internet then i couldn’t access the already read mail.
how could i Access the email with are in Back up taken by Software. Is there any Article related to back up ?

Hello Paresh,
if these mails are on your IMAP account, go to Tools>Accounts and under the IMAP tab of your account check the option to ‘Download messages for offline use’.