If the Outlook file contains attachments then you can access them by clicking on the button at the righthand edge of the toolbar in the email window. This button will display the attachments drawer.
You can then save your attachments by selecting one (or more) of them in the drawer and clicking on the Save button.
You can also drag the attachment into a supported program. For example, any attachment may be dragged into the Finder to save it. If the attachment is a picture then the attachment may be dragged into any program which supports image data - for example, TextEdit.
Please note that this button will be greyed out if the email contains no attachments.