You may need to add Charter-Spectrum to the list of evil blockers.
I've tried to point a forwarding address to a charter.net address. Nogo. In the same timeframe, I was able to get the forwarder pointed to posteo.org.
"Alexis" at Spectrum chat "support" claims it is a spamgourmet "program error".
She claims Spectrum doesn't block senders. Then again, she claims Spetrum doesn't use SMTP.
And she says they have no tech support. When asked who configures their esmtp server or sets up ip filters, she asks "is there something else I can help you with?"
Buyer beware.
Anybody set up on Spectrum lately?