In my textbook, there are instructions for a composition. These instructions are the following: こんど、国際交流協会で座談会があります。テーマは「文化や習慣の違い」です。 下のことについて、みんなで座談会の観衆尾をしましょう。
Then, a list of further specifying instructions follows, specifying various topics to talk about. One of them is the following:
で話したことをまとめてメールで送りましょう It is this で at the very beginning which I have never seen so far ^^ Mostly because I've never seen particles taking the lead position in a sentence xD Here's my attempt at translation. => "Please send the talked about things all in one piece with E-mail."
EDIT: Since some asked for more context, I uploaded a scan of the full exercise. https://www.docdroid.net/hBn7YgR/1.pdf Its number 5, チャレンジしましょう.