Admins may wonder what happens if an unsynced user attempts to chat in a channel that is synced for cross-platform messaging.

This is relevant for orgs that have set up Channel Sync but have yet to sync their users for direct messaging with User Sync.

To illustrate this concept, we will use the example of Sarah, a Slack primary user.

Sarah is a member of "test-channel," a channel that is currently synced by Mio. But, Sarah is not synced with Mio via User Sync. If she sends a message in "test-channel," will it be sent across platforms?

In this situation, cross-platform messages will not be sent natively. A native message is one that looks the same as other messages received and sent on a platform. With Mio's fallback solution, Sarah's message will be sent in an adaptive card.

Adaptive cards allow the Mio app to impersonate Sarah on her secondary platform. For the sake of this article, we will see examples of Sarah's messages sent to Webex, Microsoft Teams, and Zoom Team Chat as if she is a secondary user on each platform.

As an unsynced user sending messages in a synced channel, Sarah's messages will look like this:

After Sarah is fully synced, her message appears to secondary platform users like this:

As you can see, messages sent without adaptive cards are almost indistinguishable from each platform's regular messages. It is strongly recommended that you sync all users via User Sync to maintain a native chat experience in direct messages and channels.

It is important to note that even if users are synced via User Sync, they must be added to the synced channel on their primary platform. If not, Channel Sync will default to adaptive cards sent by the Mio app.

Synced users whose secondary platforms are Microsoft Teams or Webex must be members of those teams or spaces in order for us to post with their full accounts.

If they are synced but not members of the team or space, their messages will continue to be sent via adaptive cards.