SDP-Cloud - Looking for approval by Email solution

SDP-Cloud - Looking for approval by Email solution

Dear bros, 
My company is using SDP cloud, standard version with Service Catalogs add on. 
I'm trying to find solution for approval by email. 
I understand that the approver can come to SDP and click to approve function. But as we all known that the approver is always high level, they requires something simpler then come to SDP, and click. 
They just want to reply on email: APPROVED or REJECTED. That's it. 
As from my vendor who support us to implement this project, they said that SDP cloud cannot do that. 
I'm looking for this solution from SDP community. 
Hope that I receive good advices from all of you/
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