As of 6/2018, all Team Members (and only Team Members) have access to Channels. Team Membership provides full access to all content within the Team, including all Channel Content. Private and Shared Channels are not yet available as a feature as of 6/2018. If members are “subscribed” to the Team (similar to a Distribution Group), they will receive a copy of the email sent to the Team or Channel. Otherwise, the email is delivered to the Office 365 Group mailbox which is visible via Outlook or OWA.