You are the Office 365 administrator for a company.
You must modify the configuration of the Office 365 tenant to allow users to instant message users only with partner companies.
You need to configure Office 365.
What should you use? policy. External access policies determine whether or not your users can: view=skype-ps

A.
the Windows PowerShellSet-CsPersistentChatPolicycmdlet

B.
the Microsoft Exchange admin center

C.
the Office 365 SharePoint admin center

D.
the Windows PowerShellSet-CsExternalAccessPolicycmdlet

Explanation:

The Set-CsExternalAccessPolicy cmdlet allows you to change the properties of an existing external access
1. communicate with users who have Session Initiation Protocol (SIP) accounts with a federated organization.
2. communicate with users who have SIP accounts with a public instant messaging (IM) provider such as
MSN.
3. access Skype for Business Server over the Internet, without having to log on to your internal network.

References: https://docs.microsoft.com/en-us/powershell/module/skype/set-csexternalaccesspolicy?