Can't send email while VPN is on

I'm using EM Client as my stand alone email program. While my NordVPN is activated, I am unable to send email. I have tried using Windows 10 mail and have the same problem. If I deactivate the VPN I can send email. Working with NordVPN tech support, I tried everything, including changing SMTP ports. Nothing works. I don't want to have to use Cox Webmail. Any suggestions before I cancel my VPN subscription? Does anyone know of a VPN service that is compatible?