Since my Thunderbird downloaded and installed the latest version, 38.5.1, I am unable to send emails with somewhat large attachments. In previous version I was able to send up to a 10MB attachment with no problem. Now when I even try to send an attachment that is no larger the 2 or 3 MB it will fail, and give me an error of "connection was lost in middle of sending, please try again." I keep trying, but get same result. Never had the problem with other versions of Thunderbird. I believe there is a bug in this latest version causing this. When I send directly through my Verizon web mail there is no problem. I have used Thunderbird for years as my primary mail software and never run into this problem. None of my settings have changed. I have no problem general emails that do not have attachments. Cannot figure out why this version of Thunderbird keeps losing connection when trying to send 1 to even 8 MB attachments.