Delegate "act on behalf of" someone else in Outlook Calendar. Since calendar activity (meeting scheduling, meeting attendance, meeting changes) is handled through email, if someone is a delegate for someone else, all of the email notifications get sent to the delegate. Copies of notification can be sent to the calendar owner but for best performance, the delegate is fully managing the owners calendar.

Delegate access works very differently than designate access in Oracle Calendar. Since delegates are acting on behalf of someone else, this option should be used/chosen infrequently. By setting up "Editor" permissions, many common needs may be met. Consult with IT if you are not sure whether delegate access is the best option for you. If your supervisor and you both want to "manage" a calendar, delegate option is not the best choice, setting up specific permissions may be a better option.

Acting "On Behalf Of"

Delegates have the ability to act "on behalf of" him or her. Depending on exactly how much access they've given you, you may be able to respond to meeting requests, send out meeting invitations, and handle their email messages.

Respond to meeting requests on behalf of 

If your supervisor has giving you delegate access to their calendar, he or she can also choose to have you receive copies of emails inviting them to meetings, and messages responding to meeting invitations created by your manager (or by you on their behalf). You can respond to these messages in exactly the same way you would respond to an invitation sent to you.

Create meeting requests on behalf of your manager

Delegates can send out meeting requests on the supervisors' behalf. This is just like creating a meeting request however you must be viewing your manager's calendar in order for the meeting request to appear to come from them rather than you. If you have your supervisors' calendar open, click anywhere in your supervisor's calendar before creating the meeting request. In the Scheduling Assistant, your supervisor's name will appear. 

Use Online Mode Instead of Cached Mode

Cached Mode in Outlook is turned on by default. Cached mode provides a better experience for most users except calendar delegates. Cached Mode helps mobile and laptop users since it enables those users to continue working in Exchange while travelling and moving in and out of network connectivity. Calendar delegates who manage calendars for supervisors, particularly if doing so from a Windows desktop computer on Grounds, should use Online Mode instead of Cached Mode for a better user experience. This mode provides more accurate, up-to-the-minute info on another person’s calendar availability. (View more best practices for Outlook calendar delegates.)

To turn off Cached Mode in Outlook (only available on Windows computers), see Microsoft’s article about how to turn on or off Cached Exchange Mode for Outlook 2007 and for Outlook 2010.

Windows Outlook 2010

Mac Outlook 2011