In General it is not possible to forward an email to multiple addresses.
This command can be used to set forwarding email by an administrator:
Set-Mailbox -Identity “email@domain.com” -DeliverToMailboxAndForward $true -ForwardingSMTPAddress anotheremail@domain.com
But this command does not accept more than one email so in case of a need to forward to multiple addresses either we need to create a distribution group to use its email as forwarding address or another way is to use inbox rules e.g.
New-InboxRule “Forward to Multiple Emails” -Mailbox email@domain.com -RedirectTo @(‘x@domain.com’,’y@domain.com’)
Useful Links
https://answers.microsoft.com/en-us/msoffice/forum/msoffice_outlook/forwarding-emails-to-multiple-email-accounts/6b5789f5-56cb-4cec-97a1-44c9c1c7185d
http://www.enowsoftware.com/solutions-engine/simplified-forwarding-settings-in-office-365