The Accounts list
The Accounts list displays all of your email accounts.
Open the Email app. Tap the Accounts
List icon 
(at
the top of the screen) to display a drop-down list of all of your
email accounts.
Each account in the Accounts list displays the number of unread mail.
Tap an account to view its Inbox.
The account from which you send email by default is indicated by a red vertical line on the left side of the account when viewing your combined accounts.
NOTE
While viewing the combined list of your email messages, default email account messages are indicated by a vertical red line along the left side of the list.