Send email to all GitLab User, output will be a list user email address. You can put in your mail client and sent to all of your gitlab users

export_user_email.rb

require 'net/http'
require 'json'

YOUR_API_KEY="INPUT YOUR ADMIN PRIVATE_KEY HERE"
YOUR_SERVER_HOST="YOUR HOST"
response = Net::HTTP.get_response(YOUR_SERVER_HOST, "/api/v3/users?private_token=${YOUR_API_KEY}")
users = JSON.parse response.body
puts users.map{|user| user["email"] + ";"}