Connections
Add a mailbox by connecting it to Microsoft Outlook.
Every mailbox in TeamEmail, personal or shared, is backed by a real Outlook mailbox connected through Microsoft.

Go to Settings > Connections.
Select Connect.
Sign in to Microsoft in the window that opens, and grant TeamEmail access when asked.
Wait for the connection to finish importing. This can take a few minutes for a mailbox with a long history.
A newly connected mailbox becomes an individual inbox, visible only to you. To turn it into a shared inbox other people can work from, see Inboxes.