Have you started writing your code? The first thing I would need to know is
how are we getting access to these e-mails? Would they be part of a search
result? All currently open e-mails? Selected e-mails?
Once you get a handle to the required e-mails, all you need to do is access
the MailItem.Body property for each message and concatenate them to apply to
another message's MailItem.Body property.