What could cause all of our shared mailboxes to have "Cannot expand folder?"

We have a multi-domain office 365 account with multiple shared mailboxes on different domains with the same prefix.

eg. ap@yahoo.com, ap@yahoosistercompany.com, ap@yahooparentcompany.com

The issue is anytime we try to do these types of mailboxes and then add the mailbox to out look we get the error cannot expand folder.

Any ideas?
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You would have to give full mailbox permission to the shared mailbox.
there's a guide here.

chazzwillie15Author Commented:
I have seen this recently w/ office365 shared mailboxes not opening correctly as well. It started last week when office365 had a large outage.
It appears to be an automapping issue. I would open a case with Microsoft, however If you would like a temporary workaround, disable automapping for the shared mailbox. You'll need to do this within powershell. The command would be as follows:

1.) Add-mailboxpermission -identity <sharedmailbox@domain.com> -user <username@domain.com> -accessrights FullAccess -InheritanceType All -automapping $false

If the mailbox has full access already set, replace "add-mailboxpermission" w/ "Set-mailboxpermission.

If that still doesn't work, remove full access all together, then re-attempt step 1.   You could also use the command:
 Remove-mailboxpermission -identity <sharedmailbox@domain.com> -user <username@domain.com>

*You will need to add the mailbox manually, by going into account settings, double click the account, more settings, advanced, then "add"

To do this on a larger scale, see https://technet.microsoft.com/en-us/library/Hh529943(v=EXCHG.141).aspx

Hope this helps. Just know that this is likely effecting many people.

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