A broad consensus across experts, email marketers, and documentation indicates that a sending IP address does NOT need to accept incoming SMTP connections to achieve good email deliverability. The focus should be on domain-level checks (MX records), sender reputation, proper email authentication (SPF, DKIM, DMARC), outbound connectivity, and list hygiene. Checking for inbound connections on the sending IP is considered an outdated, irrelevant, or misguided practice.