A lead source is the channel or dataset through which a lead entered your system: an inbound form, a product signup, a referral, an event, a prospecting database export, a bought list or a scrape. Source is recorded on every record and is the single strongest predictor of data quality and conversion. Invalid rates run from 5 to 10% on inbound forms to 10 to 25% on finder exports and about one in seven on bought lists not verified within 90 days.
Source is a required field at record creation, with a controlled vocabulary so that reports can group by it. The metrics by source are volume, verification result shares, conversion rate and cost per reachable lead. A source whose invalid share rises is an entry point that needs validation.
The B2B leads guide ranks seven sources by data quality and the list websites page ranks the online sources with corpus rates.
A quarterly source report: inbound 1,200 leads at 6% invalid and 4% to customer; database export 3,000 at 16% invalid and 0.8%; a bought list 2,000 at 31% invalid and 0.1%. Cost per customer is lowest on inbound, and the bought source is dropped from the next quarter's budget.
Verify a list or a single address. 100 free checks a month, unknowns refunded.
Verify Leads - FreeAyoub built BounceZero's 5-stage validation pipeline, its dedicated BGP-announced IP infrastructure, and the Patroni HA PostgreSQL cluster behind every verification. Previously built high-volume email delivery infrastructure. Trained at 1337 Benguerir (École 42 network, 2019). Open-source: bgp_analyzer.