User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:39.0) Gecko/20100101 Firefox/39.0 Build ID: 20150629114848 Steps to reproduce: Start composing a message in Thunderbird 38.1.0, Windows 7 x64, no HTML, plain text only. Write text with leading indent) and trailing spaces such as (the following is 2 lines of 4 spaces + "Lorem ispsum" + 4 spaces): Lorem ipsum Lorem ipsum Copy the text and check the clipboard (e.g. by pasting the text in another application). Actual results: All spaces are removed except 1 leading space on the first line. Expected results: Text should be copied to the clipboard as shown in the editor. No spaces should be removed, neither leading nor trailing.

I can now confirm that this applies to Linux x86_64 too (tested on Lubuntu 14.04 x64). Spaces are lost in Thunderbird v38.1 and v40.0b1 (build 2015-07-24). Thunderbird 31.8 did not yet show this bug.