Two days ago my outgoing emails started to have question marks inserted wherever I had a double space. (I use double spaces after periods at the end of sentences.) This happened suddenly--a message I sent on 2/19/18 at 8:26 pm (PST) was fine (I could see what my outgoing message looked like when the recipient replied) and the next message I sent at 9:26 pm had double question marks after every period in my part of the message when the recipient replied. In both cases the recipients text in the replies was fine. Here is an excerpt from the first message where this showed up: Sorry for not responding sooner.?? Belated thanks for a great visit!?? Pat--socks I'm using TB 52.6.0 (32-bit) on a windows 10 machine (presumably 64 bit). I've done some troubleshooting but haven't made much progress: 1) If I change the outbound and incoming encoding from unicode to western (Tools->Options->Display->Formatting->advanced->text encoding) I get single question marks inserted, not double. 2) Here is the weird thing--I just fired up an old windows 7 laptop where thunderbird has not been used to send mail since 1/30/18 (before this problem started). Thunderbird did install an update that I must have downloaded but not installed (52.5.2 32 bit). I then sent a message and got the extra question marks, so it doesn't seem to be due to change I made on 2/19/18 on the windows 10 laptop. 3) my outgoing mail server is outbound.att.net. I also tried smtp.sbcglobal.yahoo.com (which my wife uses with a Mac with no problems) and I get the same double question marks. 4) I get this problem in newly written messages from my account and also replies. 5) I tested by reading messages in my yahoo webmail and see the extra question marks there as well as in Thunderbird. 6) I see the extra question marks if I view the raw message (in either yahoo webmail or thunderbird "view->message source".) If I create a message that has something like bullet points in it, so that the raw message has both plain text and HTML, the extra question marks are in both the plain text and HTML portions of the raw message. 7) I DON'T get the extra question marks in my signature if I put some double spaces there when I am composing the message, but in the same message I DO get the extra question marks in the body. 8) The messages in my sent folder look fine, both as displayed and when I look at "message source". 9) A few weeks ago I had a problem where if I replied to a message that came from an outlook user, the messages would get � in them. I changed the default encoding from western to unicode and that seem to fix the problem. Note--I didn't take great notes when I did this, so I don't know if I just changed the encoding at that time in the View->text encoding menu or in the options panel. 10) I don't think I changed anything to create this problem, but I may have played around with the "view->text encoding". I have two active accounts in this profile (but both use the same outgoing server). 11) I found this support thread, which gave me trouble shooting ideas: http://forums.mozillazine.org/viewtopic.php?f=39&t=2886143 It is for a similar problem, but I see the double question marks when I view the source and this guy didn't seem to. Thanks! stuart