How can I find webform e-mail submission values keys?
Here is the answer.

Lets say I've 4 fields in Webform 

&nbsp;Label &nbsp;&nbsp;&nbsp;- &nbsp; Field Key

First Name - first_name

Last Name - last_name

Phone Number - phone_number

Message - message


Here is the way to access them in template field

For example if you want to display name as the combination of First Name and Last Name

Name:  %value[first_name] %value[last_name] 


Then this appears in mail like 

Name: Krishna Mohan


If you want to access a individual field value with Label 

For example Phone number

%email[phone_number]


This appears in mail like

Phone Number - 555-555-5225


I've tested this and works great! Hope this helps