imapmbox vs. mbox

I'm using Mail.app to read mail from an IMAP account.  I'd like to 
figure out how to 'archive' my email in various folders using Mhonarc.  
I've got Mhonarc working, thanks to Lasar Liepins <lasar(_at_)liepins(_dot_)net>, 
but now I'm not able to 'convert' my .imapmbox formatted mail folders!
Does anybody know the difference in mbox and imapmbox?  Is there a way 
to get them to work with Mhonarc?
Thanks.

bw

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Bill Whitacre
bw(_at_)his(_dot_)com