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 “firstname.lastname@example.org” -DeliverToMailboxAndForward $true -ForwardingSMTPAddress email@example.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 firstname.lastname@example.org -RedirectTo @(‘email@example.com’,’firstname.lastname@example.org’)