Does anyone know how to find variable on Cards and Board?

[Shohei Mitsuhashi]

Does anyone know how to find variable on Cards and Board which is NOT on the list as shown below:

https://help.trello.com/article/1157-variables

for example: user's email address, email for this card

[Arne Albers]

Hey there,

I would also like to get the users email as a variable. To be able to send the user that triggered an action an email (via automation){usermail} does not work I guess.. Because it is not in the documentation.

Best wishes

Arne

[Iain Dooley]

@Shohei Mitsuhashi you can't get either of those things (either with Butler or with the API), but you can send an email to members of a card using Butler.

[milynnus]

@Shohei Mitsuhashi 

I have tried and I am able to get my own email but not too sure about other board members because they were all empty. They were no errors. 
I was not successful with card email.