I have been using Thunderbird for mail since about April of 2015 with no problems. I have just discovered that none of my sent messages have actually sent within the last 48 hours. The cc'd versions show in my in-box and the sent messages show up in my sent file. I have confirmed with several clients that they have not actually received anything from me. I have since send a number of test emails from different computers to a variety of email addresses and they are not making it to the recipients. We have made no changes to the way we have our emails set up. All incoming email is fine. I am receiving, but can't send. It is very difficult to do business when you can send contracts, etc. Any help is appreciated. I am not tech savvy. Working on Mac. HELP!