As you can see from the screen capture above I have added a guest user to my plan – the LU icon – email@example.com – which also happens to be me – so not a great example of collaboration – but you get the idea. We don’t yet have the ability directly in Planner to add a guest (coming soon) – but we can assign guests to tasks for guests who are already in the tenant, having been added through Teams for example (ignore the ‘2’ – I forgot to capture a screenshot when I first added me as a guest):
The important thing to remember here is that we are not federating a login with Google – and it actually creates an account in your Office 365 tenant which needs its own password – not your Google (or whatever) password – and please don’t re-use you Google password – very bad practice. The person you invite will see an e-mail (in this case in Gmail) – first verifying the e-mail address, and once you do, then you will receive an invite to Teams (in this case):
Then your guest has access to Teams and can start collaborating:
Once your guest has access they will appear to be used elsewhere – such as assigning to tasks in Planner:
One thing that may catch your guest out is the log-in Url they need to use – and for Planner just going to https://tasks.office.com will NOT work as that Url does not know which tenant you are attempting to log in to – and only accepts “work or school accounts”.
The log-in Url needs to identify the tenant – so the full Url would look something like this:
And that one will work – and the guest sees the plans and groups of which they are members.
There are some limitations on what guests can do in Planner, some based around security (can’t create plans or add other guests for example – and can’t join plans themselves) and others are more related to their possibly limited tenant capabilities (no mailbox not set with the MailUser property for example) so they cannot may not be able to comment on a task. Full details can be found on the support article at https://support.office.com/en-us/article/guest-access-in-microsoft-planner-cc5d7f96-dced-4da4-ab62-0....
Guest accounts will be listed in the Office Admin center under Users, Guests – as well as in Azure Active Directory: