How a marketing agency cleaned 1.4M contacts before a product launch

A digital marketing agency had a 1.4M-address list compiled over four years from multiple sources. With a major product launch two weeks away, they needed it validated and segmented fast.

Nexus Digital (name changed) manages email marketing for a portfolio of enterprise clients. For a major consumer product launch, they had assembled a combined list of 1.4 million addresses from client databases, co-registration partnerships, trade show leads, and legacy imports — some as old as four years. The launch was two weeks away.

The challenge

A list compiled from that many sources over four years was almost certainly dirty. The agency's past experience with combined lists had produced bounce rates of 4–6% — enough to trigger ESP warnings and jeopardise the sending account for the launch. They needed to know exactly what they had and how much of it was sendable.

The validation process

We processed the 1.4M addresses in three bulk jobs over 24 hours (to spread load and allow for re-queuing on any failures). Results: 168,000 INVALID (12%), 112,000 DISPOSABLE (8%), 182,000 CATCH_ALL (13%), and 94,000 with SPAMTRAP flags (6.7%). The safe-to-send VALID segment came out to 844,000 addresses — 60.3% of the original list.

Discovering that 39.7% of a list is unsendable is alarming — until you consider what would have happened if you'd sent to all 1.4M and hit the spam traps and hard bounces.

Segmentation strategy

The 844,000 VALID addresses were split into two tiers: high-confidence (VALID + not a role account, 680,000) and moderate-confidence (VALID but role account, 164,000). The launch campaign sent to the high-confidence tier first. The moderate-confidence tier received the campaign 24 hours later after observing initial bounce performance. The 182,000 CATCH_ALL addresses were sent a separate, lower-frequency version of the campaign to limit bounce exposure.

Results

The launch campaign achieved a 2.8% hard bounce rate on the initial VALID segment — well within acceptable limits. The ESP account remained in good standing throughout. Open rate on the high-confidence segment was 44%. The client attributed part of the product launch's commercial success to email performance, and the agency now runs all list imports through OhBounce.ai before any campaign.