Blacklists are the industry's shared lists of domains and servers caught sending spam or abuse. Land on one and your legitimate mail silently starts disappearing.
Blacklists (also called blocklists or DNSBLs) are reputation lists that mail providers consult before accepting a message. If your domain or sending IP appears on one - often after a compromise, a misconfiguration, or being impersonated - receivers may quietly junk or reject your mail.
The damage is invisible: there's no bounce on your desk, your mail just stops landing. By the time someone notices "we're not getting replies", you may have been listed for days. Catching a listing early, and knowing why, is the difference between a quick fix and lost business.
A clean sending reputation across the major lists, and an alert the moment you appear on one, so you can act before deliverability suffers. Strong SPF, DKIM and DMARC make listings far less likely in the first place, by stopping others sending abuse in your name.
Related: SPF · DKIM · DMARC · MTA-STS · TLS-RPT · DNSSEC
DMARCER watches the major blacklists for your domains and tells you the moment you appear - and what to do about it.
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