Email::Folder stuck at first message

I have tried to process messages from a Mozilla Thunderbid INBOX file.

[code]
  use Email::Folder;

  my $folder = Email::Folder->new("c:/users/eddie/desktop/INBOX.txt");

  while( my $message = $folder->next_message ) {
      print join "\n", map { $_->header('Date') } $message;
}
[/code]

the INBOX file was copied from my Thunderbird profile data and renamed.  
This above code should spit out dates of all emails in the inbox, but it 
stops after one message.  Am I doing something wrong to prevent the 
processing of the entire file?

Thanks,
Eddie Rowe