What it is
Mailspike is a dual-purpose email reputation system offering both a blocklist (BL) and a whitelist (WL). The BL lists IPs with poor sending reputation based on spam complaints, trap hits, and behavioural signals. The Z-list is a more severe zone for IPs with very high spam ratios. Mailspike also operates a reputation scoring system that can return positive scores for trusted senders.
How it affects SMTP delivery
Mailspike BL is queried at SMTP connection time by MTAs that use it. Listings result in either 550 rejections or negative scoring depending on MTA configuration. The Mailspike whitelist can override blocklist signals for senders who have applied and been verified.
What causes a listing
Listings occur from spam trap hits, complaint rates exceeding Mailspike's thresholds, or sudden volume spikes from an IP with no established sending history.
How to get removed
Mailspike listings expire automatically based on the listing severity and subsequent sending behaviour. Monitor your IP status at www.mailspike.net. Whitelist applications are available for verified senders.
For the full reference catalog, see the email blocklist directory.
Delisting process in detail
Mailspike operates two zones: bl.mailspike.net (blacklist) and z.mailspike.net (reputation scoring). Delisting is handled through mailspike.net’s removal form. Mailspike responds to delisting requests within 24-48 hours for legitimate senders and applies automatic decay when observed abuse patterns stop. The Mailspike reputation zone provides a 0-9 score rather than binary listing, giving receivers more nuanced signal. Score 0-3 typically causes rejection, 4-7 causes soft-fail or greylisting, 8-9 is considered good. Delisting effectively means moving the score above the rejection threshold.
Prevention practices
Mailspike’s algorithms weight sending volume patterns, complaint rates, and honeypot hits. Prevention requires the fundamentals: authenticated sending, disciplined list hygiene, prompt complaint remediation, and consistent volume patterns. Mailspike is one of several blocklists that reacts to sudden volume spikes on previously-quiet IPs; new IPs should follow a gradual warmup schedule (start at 50-100 messages per day, double every 2-3 days until reaching target volume). Query bl.mailspike.net and z.mailspike.net regularly for your sending IPs.
Common listing causes
Mailspike listings usually correlate with either high complaint rates on marketing sends or honeypot hits from poor list quality. Because Mailspike operates a large honeypot network in Europe and North America, purchased lists commonly hit multiple traps within the first send. Compromised shared-hosting accounts are the second-largest source: attackers hijack an account and blast spam through the shared IP, listing the entire IP for all customers on that infrastructure. Volume spikes without warmup are the most avoidable listing cause.
Related blocklists
Mailspike operates independently but correlates with Spamhaus, SORBS, and Barracuda for compromised infrastructure. Its reputation-scoring zone (z.mailspike.net) is queried by mid-market mail gateways looking for more nuanced signal than binary blocklists provide. Mailspike’s European operation gives it particular strength in EU spam patterns; senders reaching European recipients should monitor Mailspike alongside Spamhaus for regional coverage.
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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