curl --location 'https://qyapi.weixin.qq.com/cgi-bin/exmail/app/read_mail?access_token=ACCESS_TOKEN' \
--header 'Content-Type: application/json' \
--data '{
"mail_id": "MAIL_ID"
}'{
"errcode": 0,
"errmsg": "ok",
"mail_data": "MAIL_DATA"
}