How to enable/disable add-ins in Outlook 2010 and later
|Knowledge Article Number||000198676|
|Description||How to enable/disable add-ins in the Outlook 2010, 2013, and 2016|
|Resolution||Ensure that the system requirements have been met.
1. File | section Options | section Add-Ins
Options-> section Add-Ins
2. At the Manage drop down list at the bottom select which type of add-ins you would like to enable/disable.
3. Select COM Add-ins or Disabled Items depending on what list the "Salesforce for Outlook Side Panel" add-in is in then press “Go…” and make the changes
4. For some add-ins you’ll need to restart Outlook for changes to take effect.
NOTE: Important Troubleshooting in case of Add email button disappeared in the Outlook.
Additional information from Microsoft can be found here