I have one of three computers where I cannot send mail from my charter.net account on Outlook Express 6 running under Win XP Pro with all current updates and service packs installed. I receive a 421 Error any time I try to send. I have tried importing settings from both other computers that have no problem sending mail from my charter.net email account. All 3 computers use the same ISP and router. I deliberately have no firewall software, AV, or anti-malware software installed on purpose due to issues with business apps I use. (Please don't lecture me on those choices if you choose to respond). This inability to send is relatively recent, but I can't correlate it to anything in particular. I have basically the same programs installed on all 3 machines, they are used in a SOHO environment. Also, I have tried using Microsoft Outlook and Thunderbird on that machine. They do not send mail either. I've checked other message boards, and no one seems to have a definitive answer to the question. Any thoughts would be appreciated.