What it is
SpamRATS operates three DNSBL zones targeting different IP categories. RATS-Dyna lists IP ranges designated as dynamic by their ISPs (residential broadband, mobile networks) that should not be sending direct-to-MX mail. RATS-Spam lists IPs confirmed to be sending spam. RATS-NoPtr lists IPs without a valid reverse DNS PTR record, which is a basic deliverability requirement for most mail servers.
How it affects SMTP delivery
RATS zones are used in Postfix, SpamAssassin, and some enterprise mail gateways. A RATS-NoPtr listing is preventable through simple PTR record configuration. RATS-Dyna listings affect senders who bypass their ISP's outbound mail relay and attempt to send directly to recipient MTAs.
What causes a listing
RATS-Dyna: sending from a dynamic or residential IP range without an ISP mail relay. RATS-Spam: confirmed spam activity. RATS-NoPtr: no reverse DNS PTR record configured for your sending IP.
How to get removed
Use the SpamRATS portal at www.spamrats.com. RATS-NoPtr listings resolve automatically once a PTR record is configured. RATS-Dyna removals require demonstrating that the IP is used for legitimate mail submission.
For the full reference catalog, see the email blocklist directory.
Delisting process in detail
The Spamrats blocklists (spamrats.com) operate three zones: RATS-Dyna (dynamic residential IPs that should not send mail), RATS-NoPtr (IPs without valid reverse DNS), and RATS-Spam (IPs observed sending spam). Delisting is handled through spamrats.com’s removal form. RATS-Dyna and RATS-NoPtr removals require fixing the underlying issue (get the ISP to remove the dynamic-range designation, or configure a valid PTR record). RATS-Spam requires documenting remediation. Automatic decay occurs over 7-30 days depending on the zone; manual delisting is available with justification.
Prevention practices
The three RATS zones each have different prevention approaches. RATS-Dyna requires sending from static, business-designated IP ranges (not residential broadband). RATS-NoPtr requires configuring reverse DNS so PTR records match the forward-confirmed sending hostname; this is basic mail hygiene that most receivers now require. RATS-Spam requires the standard anti-abuse practices: authenticated sending, list hygiene, complaint monitoring. Query all three RATS zones (dyna.spamrats.com, noptr.spamrats.com, spam.spamrats.com) regularly for your sending IPs.
Common listing causes
RATS-Dyna listings usually mean the ISP has designated the IP range as dynamic residential, which is expected policy. Sending mail from such ranges is a strong spam signal. Fix: request a static business IP allocation, or move to a hosting provider with clean business ranges. RATS-NoPtr listings result from missing or misconfigured reverse DNS: create a PTR record pointing to your sending hostname, and ensure the hostname’s A record points back to the same IP (forward-confirmed reverse DNS, FCrDNS). RATS-Spam listings correlate with actual observed spam sending and require the standard remediation.
Related blocklists
RATS-Dyna overlaps with Spamhaus PBL for policy-based dynamic ranges. RATS-NoPtr is unique among major blocklists in specifically catching reverse-DNS issues; most others incorporate reverse DNS into general spam scoring rather than as a standalone signal. RATS-Spam is a general spam observation list similar to Spamhaus SBL or Barracuda’s RBL. Enterprise mail administrators typically monitor all three RATS zones alongside the major blocklists to catch reverse-DNS and dynamic-range issues before they cause broader reputation damage.
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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