Similar to having an assistant help you manage your incoming paper mail, you can use Microsoft Outlook to allow another person to receive and respond to e-mail messages, meeting requests and responses on your behalf. This person is called a Delegate. You can also grant additional permissions that allow your delegate to read, create, or have more control over items in your Microsoft Exchange Server mailbox.
Microsoft provides an article with details on this process:
About Delegate Access
Beyond merely sharing Outlook folders, Delegate Access enables you to grant additional permissions, such as allowing a delegate the ability to create e-mail messages or respond to meeting requests on your behalf.
As the manager, your mail must be delivered to your mailbox on the Exchange server, not to an Outlook Data File (.pst) on your computer.
You and the delegate must use the same version of Outlook.
As the person granting permission, you determine the level of access that the delegate has to your folders. You can grant a delegate permission to read items in your folders or to read, create, change, and delete items. By default, when you add a delegate, the delegate has full access to your Calendar and Tasks folders. The delegate can also respond to meeting requests on your behalf.