We are currently Slack to satisfy our mobile (mostly off-topic) chat needs, as, it seems to be working well for what we needed, with the proper security.
If you would like join in the (sometimes off-topic) chat, request an invite by sending me an email to dragon123456giru@gmail.com, just make sure to take out the 123456 part. Your email address will be shown to everyone in the group, so if you want to use a fake email to join, you may go to guerrillamail.com and get a quick one to use. The email address will be needed to accept the invite, as it is the only way to join a team on Slack.