HRBL is a localized real time blacklist provider mainly for Hungarian mail servers.
It lists those less important, foreigner, otherwise legitimate-looking mail servers that send malware to us or to our contributors. It does not matter at all why they send us malware, who sends us malware through them. Lazy ISPs, hacked servers, open relays, hijacked accounts may result listing.
It also lists hostnames and domain names that are related to Hungarian malware, and are usually not listed in the main, international RHSBL services.
Listings expire if no more malware received or can be manually delisted.
HRBL has two blacklists. Both of them are DNS based blacklist. You can use them free of charge on your mailserver just like any other blacklists. Set it up to use bl.hrbl.hu to check IP addresses and uribl.hrbl.hu to check hostnames. See more on the Usage page.
To check if a given IP address or hostname is listed in our blacklists you can use DNS queries described on the usage page, or you can use the checking page for a web based method.
These blacklists are not intended to block legitimate emails, although malware sending compromised mail servers get listed, which means their users will be unable to send emails to those hosts which use the HRBL blacklists. These users can delist their mailserver's IP addres and hostname after seeing a link in the bounce message they get back. See on the Delisting page.
Delisting is easy but be careful. Your host will be listed again next time it sends malware to us or to our contributors. After several listing-delisting cycles delisting will be temporarily suspended for that particular address or hostname.