Understand: Licensing types
A user account consists of:
Such a mailbox can be a personal mailbox, an Online Archive mailbox or both — you will only need one Veeam license per user.
Additionally, each user in your Office 365 subscription that has been granted access to team, communication, collaboration and other non-personal SharePoint sites that you plan to back up must be licensed.
Each user in your Office 365 subscription that has been granted access to Microsoft Teams objects that you plan to back up must be licensed.
The Veeam license is consumed by objects (mailboxes, OneDrive for Business accounts, SharePoint personal sites) for which at least one restore point has been created within the last 31 days. If an object was not backed up for 31 days, its license is automatically revoked.
A license is not required for:
Shared and resource mailboxes do not consume units in the Veeam license if such mailboxes do not have a Microsoft Office 365 license assigned.
An external SharePoint user is a user from outside your Office 365 subscription to whom you have given access to one or more sites, files or folders. External authenticated users are limited to basic collaboration tasks, and external anonymous users can edit or view specific documents when given specific permissions.