when you say ''paste it on message page of Thunderbird message page'', I presume you are refering to a new 'Write' message. I presume you hightled the text in the Libre Office doc, right clicked on highlighted text and selected copy, then right clicked in a new Write message compose area and selected Paste. When you say ''it dosen't respond (not active).'' I presume you mean nothing is pasted. I also presumed that you did have a new Write message open and you right clicked in the Write message compose area and selected Paste. You do not mention whether you are simply inserting a short piece of text or several pages of a document, or whether the document is just text or includes other material like tables and images etc. It is not recommended to use any word Processing package when writing an email. Word processing packages offer a more complicated/range/ different set of formatting options that are not available in HTML email formatting. This is why you have the option to Write new messages using the editing function in Thunderbird. If you need to send someone the Libre Office Doc, you should create an email and attach the document, so the the recipient can read it using the correct program and see it correctly formatted as you intended when you created it. The recipient can also choose to save the attachment to another folder. Having said that, you should be able to copy paste, but may have to accept that some formatting may be messed up or not quite correct. If you are writing in Plain text then all formatting will be stripped.