The solution can sometimes be to forward all inncoming email, and some times to an external or internal address.
Incase of beeing external address, we need to create a contact in our Addresslist:
New-MailContact -Name <Display Name> -ExternalEmailAddress <External Recipient Email Address>
Then we can forward email to this address:
Set-Mailbox username -DeliverToMailboxAndForward $false -ForwardingAddress address
You can choose wether to leave a copy in your inbox ($true) or delete it from the inbox when its forwarded ($false), or if you dont define it the default is saving a copy.