You are actually can enable or disable the plugin steps through CRM Web UI
This is the step if you use the CRM UI to disable the plugin step:
1. Go to Settings --> Customization --> Customize the System
2. In the left navigation you can see 'Plug-in Assemblies' and 'SDK Message Processing Steps'
3. Go to SDK Message Processing Steps
4. Then, you can select the plugin step you want to disable
![image image](http://lh6.ggpht.com/-2p_dmj6l65U/U8lYvWjDwBI/AAAAAAAADFs/ouNH2mSSumA/image_thumb%25255B8%25255D.png?imgmax=800)
You can select more than 1 (multiple select) as well
5. Just click the Deactivate ribbon and next to process
![image image](http://lh4.ggpht.com/-tsNiN5TqL5s/U8lYxJCuBPI/AAAAAAAADF8/ncJYb5Ev7f4/image_thumb%25255B9%25255D.png?imgmax=800)
6. You can see the status of those steps now
7. Here is the status:
![image image](http://lh6.ggpht.com/-5v63HKYw8BI/U8lYzJ5k22I/AAAAAAAADGM/4X4npVRhPLs/image_thumb%25255B10%25255D.png?imgmax=800)
Hope it helps!
Thanks
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