How to write an e-mail message as a delegate with the 'Send on behalf' permission in MS Outlook 2010

Microsoft Outlook 2010 gives you the option to send messages on behalf of another user who is inaccessible or out of office. You can do it thanks to the option to delegate permission to your mailbox called "on behalf of."

First, you need to grant permission to a particular user to use your mailbox. You can read how to do it in the article titled How to grant permission for a user to 'Send on behalf' option on Microsoft Exchange Server 2007/2010. Following this, you can send a message from Outlook on behalf of this user:

1. Click the New E-mail button on the top left corner of the ribbon.
2. In the new window click the From button (if you can't see, in the ribbon go to the Options tab, and here select "From" in the Show Fields section). 
3. Choose the option Other E-mail address.
4. You can manually type the user's e-mail address or click the From button, search and point to proper user from the default address book.
5. After you select the correct user, click the OK button.
6. Now, simply compose the message and click the Send button. 

When the recipient receives the message it will have a note that the message was sent on behalf of another user, e.g. in the From field: "User A On Behalf Of User B."