External file sharing has been giving us trouble since the B2B change. Clients reach our organization's sign-in page and get a message saying their account doesn't exist.
Does each external user need a guest account in our tenant, or should they authenticate through their own organization? And does IT have to create those guests manually?
A guest object in your tenant and authentication through the client's organization aren't mutually exclusive. The guest object represents the external user in your directory, while the user can authenticate with their own identity.
You don't necessarily have to create guests by hand. Depending on your tenant settings, sharing a file can initiate the invitation and create the guest. Cross-tenant settings can also affect how users from another organization collaborate, but trusting an organization isn't simply a replacement for guest identities.
I'd test the normal SharePoint sharing flow with one external address before building a manual provisioning process. If guest invitations are allowed, the share can create the guest as part of the process. If creation is restricted, the same workflow may fail.
Check the sharing settings at both the organization and site level, plus who is permitted to invite guests. The sign-in error alone doesn't tell you which setting is responsible.
There's a governance tradeoff here. Automatic guest creation is convenient, but it can leave you with a lot of external accounts to review. If you need tighter control, route access requests through IT approval and use automation to create or invite guests, for example with Power Automate and Microsoft Graph.
That adds friction for staff, so decide whether the approval requirement is worth it for the content you're sharing.
Keep the sharing scope in mind too. Rather than opening external sharing broadly, you can restrict where it's available and use the normal sharing menu for the files clients need. That won't fix a failed invitation by itself, but it makes the access easier to contain.
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Vexlin.39:
Users can invite external people already, but the client still gets an account not found message at our sign-in page. What would you check first?
morrowless-kiosk:
Check whether the invitation actually created a guest and whether the recipient completed redemption. Then review your external collaboration and cross-tenant access settings for anything blocking the flow.