To assign a task to someone else, add an Email address to the To field:
When you save or update a Task, a Task Assignment request is sent to the specified address. If you want to compose or update a Task without sending a Task Assignment request, disable the Send Requests option.
The Task composing page displays a list of those to whom the Task is assigned, along with their confirmation status data. When your receive replies to your Task Assignment request (see below), the confirmation status data is updated. You can also set the status manually if the person has replied with a non-calendaring E-mail that cannot be processed automatically, or if a reply has come by other means, such as a phone call.
Click the Save button to store the Task and, optionally, to send a Task Assignment request. If you have opened the Task composing page using a link on a Tasks view page, the newly created Task is stored in that Tasks folder (Mailbox). Otherwise the newly created Task is stored in your Main Tasks folder.
You can open an existing Task item in your Tasks folder, and click the Edit Task link to update the Task data. When you save the updated Task, a Task Assignment request is sent again (unless you disable the Send Requests option).