This blocklist is no longer operational. DNS queries return NXDOMAIN. Remove from MTA configurations to avoid query timeouts.
What it is
MSRBL (Mail Spam Realtime Blacklist) was an independent blocklist covering IPs involved in phishing attacks and spam campaigns in the late 2000s and early 2010s. It has been discontinued and its DNS infrastructure is no longer operational.
How it affects SMTP delivery
No impact. DNS queries to MSRBL zones return NXDOMAIN. MTAs with MSRBL in their configuration should remove it to avoid unnecessary DNS lookup timeouts.
What causes a listing
N/A, defunct.
How to get removed
No removal necessary. Remove MSRBL from any active MTA or SpamAssassin configurations to avoid DNS timeout delays.
For the full reference catalog, see the email blocklist directory.
Delisting process in detail
MSRBL (Media Steward RBL, spam.dnsbl.sorbs.net’s predecessor pattern) targets observed spam sources. Delisting is handled through the operator’s portal. Automatic decay applies when the observed abuse pattern stops, typically within 7-14 days. MSRBL is a smaller-scale blocklist with regional focus rather than global deployment. Delisting response times are typically within 24-48 hours for well-documented requests.
Prevention practices
MSRBL prevention follows standard anti-abuse fundamentals: authenticated sending, list hygiene, complaint monitoring. Because MSRBL is a smaller list, its impact is limited to receivers that specifically query it. Monitor MSRBL alongside major public blocklists (Spamhaus, Barracuda) for comprehensive coverage. Gradual IP warmup and confirmed opt-in remain the primary prevention practices for any spam-source blocklist.
Common listing causes
MSRBL listings correlate with observed spam patterns. Common causes include purchased lists that hit MSRBL honeypots, compromised shared-hosting accounts sending spam through the listed IP, and volume spikes without warmup. Because MSRBL operates a smaller honeypot network than major blocklists, listings often indicate specific abuse rather than broad reputation issues, making them easier to remediate once the root cause is identified.
Related blocklists
MSRBL operates alongside other regional and smaller-scale blocklists. Enterprise reputation monitoring combines MSRBL with major blocklists (Spamhaus, Barracuda, SpamCop) for comprehensive coverage. Because smaller blocklists sometimes list independently before consensus lists react, they can serve as early-warning signals. However, for most senders, monitoring the major public blocklists provides sufficient signal without needing to query every smaller list.
About the Author
Alaa · LinkedIn
Email infrastructure specialist with 8+ years of hands-on experience in SMTP, deliverability, and email verification. I’ve configured and troubleshot mail systems across Postfix, Exchange, and cloud relays, managed IP reputation and warmup campaigns, and built verification pipelines processing millions of addresses. My work spans DNS authentication (SPF, DKIM, DMARC, BIMI), bounce handling, blocklist monitoring, and compliance frameworks including CAN-SPAM and GDPR. I write every article on SMTPedia to give email professionals, developers, and marketers the accurate, RFC-grounded reference they need.
About SMTPedia
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