As a solution you can do the following:
1. Unpin this thing from taskbar.
2. Go to Office folder
C:\Program Files\Microsoft Office\Office14
Or Program Files (x86) if you installed it there.
3. Find OUTLOOK.EXE , Right click - Copy.
4. In the same folder Right click - Paste Shortcut.
5. PIN THAT shortcut.
If you try to pin exe files itself, you will get missing icon. So you need to pin a shortcut that you will make yourself.
My Computer
At a glance
Windows 8.1 ; Windows 7 x86 (Dec2008-Jan2013)
Computer type
PC/Desktop
OS
Windows 8.1 ; Windows 7 x86 (Dec2008-Jan2013)
Other Info
"The scale icon at the top right of a post or tutorial is how you can give rep to the member."