Synced users on Mio get the most benefits out of their Mio experience. When a synced employee sends a message into a channel, they'll appear as a fully native user. This means that Slack users messaging people on Microsoft Teams will look just like anyone else on Microsoft Teams, and vice versa.
On the other hand, if a non-synced user attempts to send a message into a synced channel, they'll have a "message sent on behalf of" notification next to their avatar, and people may be unable to see their profile picture.
Syncing simplifies the Mio experience and makes interacting between channels seem more natural. Before syncing, an employee using Slack who hasn't set their primary account would look like this in Microsoft Teams.
After syncing and confirming their primary account, this is how employees using Slack will appear on Microsoft Teams:
Additionally, when someone tries to send the non-synced person a DM, they'll receive an alert from Mio asking them to "sync now" to receive the content:
Similarly, if a non-synced person tried to DM a Microsoft Teams primary synced employee using Slack, they would receive another message asking them to sync:
Once the employee clicks on "Sync Now" button and completes their primary channel sync, they'll receive a "success" notification on their primary channel, like so: