DNSBLs (DNS-based blacklists) are real-time lookups against curated lists of known mail abusers. Listing on a major DNSBL typically results in inbound rejection at receiving servers; even minor DNSBL hits can reduce inbox placement.

Blacklist Lookup for mailgun.net

Listed

IP address	Barracuda	SpamCop	UCEPROTECT L1	UCEPROTECT L2	PSBL	Mailspike	Spamhaus ZENSpamhaus ZEN combines SBL, CSS, XBL, and PBL. A ZEN listing is the highest-impact DNSBL signal. Learn more →
34.36.182.139	OK	OK	OK

This domain's mail servers appear on one or more blacklists.

The hits above show which DNSBL zones return a positive response for this domain (or its mail-sending IPs). Each zone has its own listing methodology and reputation; some are aggressive (fast to list, slow to delist), others are conservative.

A clean result is the goal — zero listings across all checked zones. If listed, follow the specific zones delisting procedure (linked from the zone name). Check whether your sending volume, list-hygiene practices, or recently-rotated infrastructure triggered the listing; address the root cause before requesting delisting.