Just a though on a new mail attachment way :).
What if we could attach existing attachments in our mailbox to new mails that we want to send.Forwarding the mail that had the attachment might not be a good solution in many a cases.
The key point here is that attachments should be like a resource,that can be shared across mails,that can be deleted edited or updated.
There could be a small widget showing all attachments that you have in your mailbox,from which you can add whatever you want to your current mail.
I think this would be a cool feature in the present email system.
You would not end up uploading the same file again and again :)
Feel free to comment on this idea ::)