When your VPN is disabled, your E-mail client is sending an IP-address that was supplied by Charter to Charter's mail-server, to authenticate your request to send/receive E-mail.
When your VPN is enabled, your IP-address is sent to the VPN-server, and the VPN-server sends its IP-address to Charter's mail-server. Then, Charter's mail-server does NOT authenticate the IP-address of the VPN server. Thus, your E-mail usage is blocked.
Check your E-mail configuration, so that it sends your Charter E-mail ID and the associated password before trying to send/receive E-mail. That IP/password will be passed "through" the VPN-server, and Charter's mail-server will authenticate your E-mail client.
So, it is possible to send/receive E-mail when the VPN is active. Nice!