However, Gmail has been so excruciatingly slow that a month ago, I've switched back to Outlook (Outlook for Mac 2011), and haven't looked back since. It feels really good to use an email client again that responds to what I do instantenously. Web email clients still have a way to go.
The whole local e-mail folder can be backed up to your favourite online backup if you feel that it's not safe to keep just a local copy.
It appears to me that FF4 is merely displaying the clipboard image in the rteditor in draft mode, but it is not actually attached to the email when sent.
Content-Type: multipart/alternative; boundary=000e0cd3282edb3e4e04a04d2812
Content-Type: text/plain; charset=ISO-8859-1
Content-Type: text/html; charset=ISO-8859-1
I may have jumped the gun here...
Since the src of the image is inline, you can save/send it as part of the HTML output of the editor - no attachments or separate upload is needed.
Having looked into what gets sent, it is definitely a Firefox thing, but for me, it only started doing it with 4.0, so hence this post.
Win+S (OneNote screenshot feature)