Yes; however, when you change an email address, mail sent to the original address will be returned to the sender (unless you've activated your catch-all mailbox). If you edit the email address, be sure to notify the user.
To edit a user's email address:
Visit your Email Control Panel.
Click the "Edit User" link for the user you'd like to edit.
Email Control Panel - Edit User Link
On the Edit User page, click "Change email".
Email Control Panel - Change Email Link
In the pop-up dialog box, enter the new email address and then click the Save button.
Email Control Panel - Change Email Address Dialog Box
Note: If a user's status is still pending, you cannot edit the user or associated email address. As soon as the user activates the address, you can edit the account.