User Agent: Mozilla/5.0 (Windows NT 6.1; rv:15.0) Gecko/20100101 Firefox/15.0.1 Build ID: 20120905151427 Steps to reproduce: Date : 2012-10-13 Object : Thunderbird 15 Japanese edition Windows edition Environment : Windows XP Professional SP 3 Japanese edition / Windows 7 Home Premium SP 1 Japanese edition Procedure : - You start Thunderbird in safe mode (because you can prevent effects of add-on). - You make a new E-mail. - You edit simply. The sentence is noncommittal. For example, add "a". - You add a certain attachment file. - You save it. - You open it, and edit a little. For example, add "a" again. - Save it again. - You open it again. - You can confirm that a new-line mark is added to the end of the mail. - If you repeat above-mentioned actions (edit and save), a new line adds definitely. So, you repeat it 100 times, you can look 100 new-line marks. Recurrence rate : 100% Confirmed profile number : I confirmed this bug in 2 profiles. Addition : I confirmed that the bug occurs in other person in Japanese forum (http://forums.mozillazine.jp/viewtopic.php?p=47205#47205). Actual results: A new-line mark is added to the end of the mail. Expected results: The E-mail should keep the original message.