Remove old email account first
Open Mail, and then do the following:
On the Mail menu, click Preferences. On the Accounts tab, select the account you would like to remove and click Add - to remove the account
Open Mail, and then do one of the following:
If you've never used Mail to set up an email account, the Welcome to Mail page opens. Go to step 2.
If you've used Mail to create email accounts, on the Mail menu, click Preferences. On the Accounts tab, click Add to open the Add Account window.
In the Welcome to Mail or Add Account window, do the following:
In the Full Name box, type the name you want to display to people who receive your email messages.
In the Email Address box, type your primary email address.
In the Password box, type the password for your email account, and then click Continue.
The Mail program uses the information you entered to try to set up your email account automatically.
Next choose the Mac apps you want to use with this account. Available choices are Contacts, Calendar, Notes, and Reminders.
Click Done to finish setting up your account.