The problem
Mailing-list hygiene is the most-deferred maintenance task in marketing. Bouncebacks tank deliverability; disposable-email signups poison conversion data; the existing “email verification” vendors charge per check at scale. We wanted a self-hostable, single-endpoint service that solved 90% of the problem cheaply.
What we built
Email Cleanup is a FastAPI service backed by SQLite. It maintains a curated domains.txt of known disposable, role, and parked providers; runs deterministic syntax and MX-record checks; and answers a single POST /validate with a structured verdict per address. Bulk endpoints accept lists and stream results back as soon as each one resolves.
The automation angle
The domain list is the product. We auto-update it from public disposable-domain feeds with a manual review queue, and accept user-flagged domains via a single endpoint. There’s no LLM here; there doesn’t need to be. Pattern matching with good source data beats clever models for the cost-per-call this product targets.
How it’s used
- SaaS signups rejecting disposable inboxes before they pollute the funnel.
- Email senders cleaning lists before a campaign goes out.
- Internal tools across our portfolio that need a fast yes/no.
What it taught us
Not every product needs AI to be valuable. Sometimes the win is a tight schema, a maintained data file, and a service that responds in under twenty milliseconds. We use Email Cleanup ourselves — it’s the kind of unsexy infrastructure that quietly improves every other product.