I'm seeing this same issue from another Digital Ocean VM. I've got SPF configured property, DKIM configured property and rDNS also configured properly. My VMs IP address is not on any well-known spam blacklists, that I'm aware of. And I've already tried to de-list my VMs IP address with the Comcast but merely get:
"Blocklist Removal Response: After investigating the issue, we have found that the IP you provided for removal is currently not on our blocklist"
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