User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7 Build Identifier: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.1.7) Gecko/20100111 Thunderbird/3.0.1 When copy/pasting into an email while composing undo will not remove or undo a pasted block of text. Reproducible: Always Steps to Reproduce: 1.compose email 2.copy text 3.paste text 4.click undo 5.pasted text remains in email. Actual Results: it would not remove the pasted text from the email I was composing. Expected Results: I expect undo to reverse the last action performed. In this case remove pasted text from email composition.