Is it possible to create a channel in Slack and set the default notification preferences for (other) new users joining the channel?
I need this in order to automatically join to certain channels users with relatively low technical skills, but to have the notifications automatically muted for that channel so that it doesn't annoy them too much.
I believe you're looking for this:
https://{your_slack_team}.slack.com/account/notifications#channel_specific_settings