Converting an existing Exchange Online user mailbox into a shared mailbox allows multiple employees to manage correspondence while preserving its existing messages, calendar information, and mailbox content.
Option B is correct because it satisfies the storage, access, and sender identity requirements.
The critical consideration is the mailbox size. Mailbox1 contains 72 GB of data, exceeding the 50 GB storage limit for an unlicensed shared mailbox. Microsoft requires an appropriate license, such as Exchange Online Plan 2, to increase a shared mailbox ' s primary mailbox capacity to 100 GB.
Consequently, the mailbox must retain suitable licensing after conversion.
Full Access permissions allow support users to open Mailbox1 and manage its existing content. Send As permissions enable users to send replies that appear to originate directly from support@contoso.com, without displaying the individual delegate ' s identity.
Option A is incorrect because removing the license would leave the 72 GB mailbox above the unlicensed shared mailbox storage limit.
Option C is incorrect because Send on Behalf displays the delegate ' s identity and also proposes removing the required license.
Option D does not preserve the existing mailbox as a shared mailbox with the specified delegation permissions.
The appropriate configuration is therefore to convert Mailbox1, grant Full Access and Send As, and retain the necessary license.
Microsoft References:
https://learn.microsoft.com/en-us/microsoft-365/admin/email/convert-user-mailbox-to-shared-mailbox
https://learn.microsoft.com/en-us/microsoft-365/admin/email/about-shared-mailboxes
