Although it can be done, it does look a little bit complicated. See "Outlook: Send To Mail Recipient opens an Outlook plain text message" from Microsoft:
The methods described use the simple Messaging Application Programming Interface (MAPI) function MAPISendMail(), which does not use the Outlook default message format. This function always creates a plain text formatted message.
To work around this issue, change the Sendto function to use the Outlook default message format, for example, Rich Text Format (RTF) or Hypertext Markup Language (HTML). (To set the Outlook default message format, click Options on the Tools menu, click Mail Format, and in the Send in this message format list, click the format that you want to use.)
To change the Sendto function to use the Outlook default message format, you need to create a shortcut in the Send To folder that calls an Outlook formatted message window:
- In Microsoft Windows Explorer, double-click to open the Windows\SendTo folder.
Note If you are using Windows XP, or later, the \SendTo folder is located in the following path: %userprofile%\SendTo
- Right-click the background of the Contents pane (the large pane on the right), point to New on the shortcut menu, and then click Shortcut.
- Type the path to the Outlook.exe file, or click Browse and to browse to the Outlook.exe file.
- Type a space followed by /c ipm.note following the last character on the command line, for example:
"C:\Program Files\Microsoft Office\Office\Outlook.exe" /c ipm.note
Note that the /c switch is outside the command line quotation marks.
- Click Next.
- Type Mail Recipient Using Outlook in the Select a name for the shortcut box, and then click Finish.
To test to see if the Sendto function uses the Outlook default message format, right-click a file on the Windows desktop, point to Send To on the shortcut menu, and then click Mail Recipient Using Outlook. An Outlook e-mail form should open that contains only the file as an attachment.