Guides for technical senders, marketers, and support teams living in SMTP.
Deep dive on bounces, spam traps, list hygiene, and why buying "targeted" lists is asking for pain.
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Old exports, scraped trade-show badges, purchased "B2B intent" databases, and recycled suppression files sneak into CRMs every quarter. Without automated validation, they hitch a ride on the next bulk send and nuke your SMTP reputation before meaningful revenue shows up.
ISPs and blocklist operators seed traps everywhere. Pristine traps never signed up for anything. Recycled traps used to be legit but were abandoned and monitored. Dirty lists hit both. Once you trip enough traps, blocklists light up and your cold email tool quietly throttles or suspends you.
Anything above a 2% hard bounce rate signals poisonous data. Dirty lists routinely spike bounce rates past 10%, which mailbox providers read as "no consent". Reputation tanked? They don't care whether marketing or sales clicked send - the entire domain/IP inherits the penalty.
Use real-time form validation, double opt-in, and automated enrichment pipelines that reject anything flagged by verification APIs. Layer in cadence rules so cold email teams can't re-import suppressed contacts. The tooling that keeps data clean costs less than digging out from a spam-folder sentence.
Bad data poisons good campaigns.
Spam traps watch for sloppy senders.
Invest in hygiene tooling before ramping volume.