Is “Sender Score” still relevant?

Still Useful. Sender Score (now from Validity) provides IP reputation insight but is not the only or most important metric. Major providers have their own reputation systems.

Gmail Postmaster shows Gmail specific reputation, which matters most for Gmail delivery. Sender Score indicates how Validity's data sees your IPs.

Use Sender Score as one data point among many. Monitor provider specific metrics where available. No single score tells the complete deliverability story.