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Please see the following for the updated information on this subject: You can call Microsoft 365 support and have them delete the user’s existing SMS notifications in order to bring the mailbox into compliance with licensing terms.Update : The information in this blog post is now outdated. SMS notifications: Existing SMS notifications are left in place, but new ones can’t be created.You can call Microsoft 365 support and have them delete the user's rules on your behalf in order to bring the mailbox into compliance with licensing terms. Inbox rules: Existing inbox rules are left in place but they are not editable.Mailbox size: If the size exceeds 2 GB, the action will fail.
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For the smoothest transition, you should delete the user’s inbox rules and SMS notifications prior to assigning them the new subscription.
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This will automatically update the user’s capabilities in Exchange Online. In the Microsoft Online Services Portal, you can assign the user a new subscription and remove the old one. The procedure for purchasing new subscriptions and cancelling old ones varies check your specific license agreement for details.
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If the user has a total of more than 50 GB of data in the primary mailbox plus the archive, the conversion will succeed, but the mailbox will be out of compliance from a licensing perspective until the excess data is deleted by the user. Mailbox data: All data in the user’s mailbox and archive is preserved.For the smoothest transition, you should remove any In-Place Holds from the user’s mailbox prior to assigning them the new subscription.
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