source: http://office.microsoft.com/en-us/outlook-help/command-line-switches-HP001003110.aspx?redir=0

/c messageclass

Creates a new item of the specified message class (Outlook forms or any other valid MAPI form).

Examples:

• /c ipm.activity creates a Journal entry
• /c ipm.appointment creates an appointment
• /c ipm.contact creates a contact
• /c ipm.note creates an e-mail message
• /c ipm.stickynote creates a note
• /c ipm.task creates a task