After updating my Monzilla Thunderbird program all my mail "sending" would not work. Not any of the 3 providers. In-coming was fine, but out-going did not work. I got an error of VO1 and comments about sending spam. Prior to the update, all worked fine. Shut my VPN off, AV and Firewall not changed. Note: I build my own computers, made gaming systems, have my own home server, and more.... so despite being nearly 70 years, been around computers since the Altair days. After the update.... spent some time pulling my hair out trying to resolve this problem. I am running Windows 10 Pro (latest updates) with 32GB RAM and all the normal crap.... computer works fine. '''Resolve''': What i found was when the "scroll lock" button was (ON), I guess I accidentally hit the button, my Monzilla TB mail would not send, only receive. THIS IS CRAZY !!! Anyway, after turning "off" or disable the Scroll Lock key on my keyboard.... Monzilla mail worked again sending normally. This one is for the Birds... but it fixed my problem. I am not a programmer, only end user and reporting what happened to me.