v1.50.99 — 2026-08-19

• feat(rbl): RBL IP Check tool on the RBL/DNSBL page — enter any IP address and instantly verify it against all active IP DNSBLs via live DNS lookup; shows per-provider hit status and return codes; new backend endpoint POST /api/v1/mail/rbl-providers/lookup with IPv4 and IPv6 support (1.50.99)