G'Day Raymond
I use Thunderbird exclusively and the e-mails I'm referring to are just the everyday type we all receive from wherever. Most are plain text but it seems that e-mails are quite different in structure from other types of documents, eg, a word processor documents, which can simply be attached to a new e-mail and sent off to another person. Although I send out and receive lots of e-mails I have no idea about their nature or structure and so I guess that's why they're forwarded rather than sent as attachments. It just seems an untidy way to have to send out a copy of an e-mail.
Best regards
James