I have been using Thunderbird 38.4.0 for 6 months minimum, using mostly the default settings, 1 add-on, with no configuration changes in at least 2 months, successfully. All outgoing e-mails are fine, all sent-folder messages are fine, all sent-folder messages Sources look fine, and all inbox messages look fine. All communication is with US English-speaking people, and my writing habits have not changed. I use, and have always used 2 spaces after a period, when creating an e-mail. Recently I have been receiving messages with extra question marks injected into sentences. They all seem to occur whenever there are 2 or more spaces in the text. Upon reading support issues, I have changed options from whatever, to "Unicode" at "Toolbar - Tools - Options - Display (group) - Formatting (TAB) - Advanced (button, click) - Character Encodings (section) - Outgoing Mail & Incoming Mail"; and checked "When possible, use the default character..." (that was unchecked upon starting this troubleshooting). That did not work. I then changed the same options to "Western"... to no avail. I created test messages to myself, to test each situation. When I look at the Sent message Source, there ARE NO injected question marks (although when I started troubleshooting, some of my test messages DID have injected question marks. After changing to "Unicode" and/or "Western", new message sources were good). When I receive the message, one question mark (?) is injected where I had 2 spaces, and 2 questions marks (??), leaving 1 space between the question mark and the beginning of the next word. Here are the outgoing good test, and the received bad test: "this is test 3. There are 2 spaces before this sentence, and 3 spaces after the comma." and "this is test 3.? There are 2 spaces before this sentence,?? and 3 spaces after the comma." Like I said, this phenomenon is NEW. No changes, no updates. So how can I start receiving message accurately again? Any why has something changed?? hoodini