Well, since no one answered this in the 5 months since the original post, I'll try.
If you mean in the native mail app, you can not. However, the messages do not delete from your mail box, unless you delete them. You can always use the browser to access them. Or simply copy the message to a note in Evernote, or another document.
edit: well, I just tried it and this does seem to work. I tried it with my Hotmail account. Hotmail was setup using the standard setup.
They are marked differently. I can't tell what folder they are in, but they are there. I can't say the same if you use another mail system or have it configured using Advanced setting (POP,IMAP, etc.). I don't really use my Hotmail account for much so I don't have a lot of messages. I simply switched from my default of 7 days to 3 days and back.
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