Greylist is not Invalid
Temporary SMTP deferrals should be retried, not graded as dead. Here's what happens when verifiers get it wrong.
Notes on data quality
Practical guides on deliverability, dialing, and shipping from the DMPHub team.
How to spot a parked domain in three checks
Nameservers, parking IPs, and for-sale page copy: the signals that separate a real business from a placeholder.
Why ZIP + city mismatches should fail
20500 is Washington, D.C. An address that says Miami with that ZIP is a red flag, even if the street exists.
