You can easily change your Email Account Properties. To do so, click the 'Tools' menu (shown in red), then 'Email Accounts…' (marked in blue).
Select your Account, and then click 'Properties' (marked in red).
In the 'General' tab of your Email Account properties (as seen below), you can change the following:
- Account Name - Name that shows in your Email Account list.
- Display Name - Name shown on Outgoing Messages.
- Email Address & Reply - You may change the Reply address if you want recipients to send replies to another address.
- 'Include this account...' - Uncheck to temporarily disable incoming messages for this account.