Podesta was copied on that email. You have to look at the source:
From: Anne-Marie Slaughter
To: Hillary Clinton
CC: Huma Abedin , Jake Sullivan ,
Cheryl Mills , Robby Mook ,
John Podesta
Subject: Don't let New York donors push you into doing an Al Gore
Date: Sat, 9 May 2015 21:10:44 +0000