Desculpe por uma resposta negativa, mas diz:
Sorry, no. You'll need to size your images prior to placing them into your Outlook message.
the Windows version of Outlook has had many years and versions to incorporate features. The Outlook for Mac version is new as of Office 2011 and not everything could be included. Sending feedback to Microsoft will allow them to prioritize development of feature requests from users.
A resposta parece ser: Envie sua opinião e espere para o futuro.