Slack API: Retrieve all member emails from a slack channel

Provided you have the necessary scopes you can retrieved the emails of all members of a channel starting with the channel name as follows:

1. Call channels.list to get the list of all channels and to convert the channel name to its ID
2. Call channels.info of the desired channel with channel ID to get the list of its members.
3. Call users.list to retrieve the list of all Slack users including their profile information and email
4. Match the channel member list with the user list by user ID to get the correct users and emails

Note that this also works for private channels using groups.list and groups.info, but only if the user or bot related to the access token is a member of that private channel.

Update 2019

Would strongly recommend to rather use the newer conversations.* methods, instead of channels.* and groups.*, because they are more flexible and they are some cases where the older methods will not work (e.g. converted channels).

Note: channels.list, channels.info, users.list are deprecated (retire and cease functioning on November 25, 2020).

Replace to conversations.list, conversations.members, users.info

You can get the email like this way:

conversations.list - Get the list of Channel Id (public or private)

conversations.members - Get the list of Member Id by Channel Id

users.info - Get the Email by Member Id

Here's a version that works with Python 2 or 3 using up-to-date APIs.

import os
import requests

SLACK_API_TOKEN='xoxb-TOKENID' # Your token here
CHANNEL_NAME='general' # Your channel here

channel_list = requests.get('https://slack.com/api/conversations.list?token=%s&types=%s' % (SLACK_API_TOKEN, 'public_channel,private_channel,im,mpim')).json()['channels']
for c in channel_list:
    if 'name' in c and c['name'] == CHANNEL_NAME:
        channel = c

members = requests.get('https://slack.com/api/conversations.members?token=%s&channel=%s' % (SLACK_API_TOKEN, channel['id'])).json()['members']

users_list = requests.get('https://slack.com/api/users.list?token=%s' % SLACK_API_TOKEN).json()['members']

for user in users_list:
    if "email" in user['profile'] and user['id'] in members:
        print(user['profile']['email'])

Note that you'll need to create a Slack App with an OAuth API token and the following scopes authorized for this to work for all of the various types of conversations:

channels:read
groups:read
im:read
mpim:read
users:read
users:read.email

Also, to read from private channels or chats, you'll need to add your app to the Workspace and "/invite appname" for each channel you're interested in.