Limitations of Google Chat

Google Voice and Google Fi

• Google Voice and Google Fi are not currently available through Chat:
  • Users who already have a Google Voice account can access Google Voice at voice.google.com, by selecting Voice from the App launcher, or by downloading the Google Voice app (Android, iOS).
  • Google Fi users must use the default SMS app on their mobile device to send and receive SMS messages.

Group Messages 

• Group messages from classic Hangouts (including their history) will not be migrated to Chat. Users can still access these group messages in hangouts.google.com. If you have important group messages in classic Hangouts, we recommend that you recreate them as Rooms in the new Chat.
• Group direct messages and rooms that are started in the new Chat will not send messages to users who are still on the classic Hangouts apps.
• You cannot add external users to Group Messages (but you can use Rooms)

External Users

• You can add external users to Rooms but not Group Messages: Create a new Room and check the box to allow people outside the organization to join.
• Users in G Suite organizations that have not yet turned on Chat won't be reachable through Chat. Users can message any external users in organizations that have Chat turned on. (Users can still use hangouts.google.com for external chats and the classic Hangouts bot will notify users of any missed messages through Chat.)
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For more information on limitations, see Google Chat known limitations.