Thia action involve registry editing, be sure to backup registry first.

1. Go to Start < Run < type "regedit".
2. Browse to HKEY_CURRENT_USER\Software\Microsoft\Shared Tools\Outlook\Journaling. 
3. To add new journal entry, right-click Journaling, press >New>Key.
4. Type the name for the entry type.
5. Add two values to entry.
A string value for text that will appear in the Entry Type field of the Journal Entry. It doesn’t have to be the same value as the registry key, but may be easier if the description is the same as the key name.
Icon string value starting 1 to 23 that will appear in the ([""]) sign.
if typing Number 24 and above a yellow envelope will apear.