Outlook 2011 Export/Import Issues

Yesterday my mother in law asked me if I could archive her email for her.  She uses Hotmail and views it in Outlook 2011 for Mac.  I used the export function within Outlook, created the .olm file with all her emails, removed them from hotmail, and then imported the .olm back into Outlook.  At first glance it appeared that everything was fine.  Fast forward to this morning and she informed me that while all the email headers, To/From, and subject lines were indeed there, the majority of emails contained no messages.  There is no rhyme or reason to which emails have message content and which ones don't.  

Can anyone help?

Thanks