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Cleaning a HubSpot or Mailchimp export

An export is not a mailing list. It is a database dump that includes unsubscribed, bounced, deleted and never-confirmed contacts, plus internal properties you should never send to an ESP. Cleaning starts with filtering on status, not with dedupe.

Then normalise and dedupe on the address, and verify domains. The order matters because filtering changes which duplicates you need to resolve.

Mailchimp exports

One row per address, with a status column — subscribed, unsubscribed, cleaned, pending, transactional. Only subscribed belongs in a marketing send. cleaned means the address hard-bounced previously; re-importing it is a guaranteed repeat bounce.

HubSpot exports

Contact exports can include lifecycle stage, marketing contact status, and a pile of internal IDs. HubSpot distinguishes "contacts" from "marketing contacts" — only the latter have a marketing subscription. Exporting all contacts and emailing them is the single most common consent violation in B2B tooling.

Strip before you upload

Remove internal owner IDs, pipeline values, and any free-text notes. They are noise in a mailing tool, and personal notes about a customer in a marketing platform is a data-minimisation problem you do not need.

Then clean

Normalise, dedupe (a person can exist twice after a merge — once on the old domain, once on the new), repair typos, drop role addresses if this is a nurture send, and check MX. Exports are usually cleaner than scraped lists but heavier on duplicates, because CRMs accumulate them by design.

Common questions

Last updated 2026-10-23.