You can get a small window in the "original" mail headers of Lotus Notes emails by going to the "Properties" tab of a document and there selecting the "ruler" tab. There you get a small window which shows the textual representation of (for example) the "Body" property.

Lotus Notes is "just" a document store with some predefined properties and rendering. Notes emails have a different internal representation and don't necessarily look like the mails you receive after they go through MIME encoding.

Also see getnotes.pl, Extract Lotus Notes Mail to HTML