# IP blacklist check
> DNSBL lookup for a public IPv4 address, via DNS-over-HTTPS.
The check asks a few public DNS blocklists through Cloudflare DNS-over-HTTPS (1.1.1.1). Results are cached for one hour, keyed by the address you asked about. Being absent here does not mean every mail server will accept mail from the address.
## Questions

### What does a blacklist hit mean?

The list published a 127.0.0.0/8 answer for the reversed address. Spamhaus can also answer 127.255.255.x when it refuses a query from a public resolver. That row is a refusal, not a listing.