Get those lost e-mails back ???
The first time you set up an existing email account in the Mail App, the
significantly lesser number of e-mails showing up might send you into a panic
attack. Do not worry; a default sync setting is to blame. Right click or long
touch on your Account in the sidebar on the left and go to Account Settings -->
Change Mailbox sync settings. Here, in the list under Download email from , select
anytime. Go back to your inbox to see all your e-mails once the sync is complete.