There are times when you may wish to save a file to disk, or view it with an external program. In particular, when people send attachments, you need to save or view to see them, as they won't appear automatically in the View window. To do this, either select 'Export Message' from the Messages menu when the message is selected, or select the 'Export' button on the View window of a message.
A window appears displaying the various parts. There will always be 'Entire Message' and 'Headers', and then all the parts. Usually there will just be one, but multipart MIME messages will contain several parts. Select the part you wish to save or display, and then click the appropriate button. You should configure the external programs in the 'Program Settings' window (under MIME).
You can also view the parts more easily from the View Window by going to the 'Attachments' tab, and doubleclicking on a section there, or select from the Attachments menu. For more information about the Attachments menu, see the 'Attachments Menu' section under the View Window page.