Migrate from Microsoft Dynamics 365 Sales to Mailchimp

Discovery and contact audit

We audit the Dynamics 365 environment via the Dataverse Web API, extracting record counts for Contacts, Leads, Accounts, and any active custom fields on Contact. We identify duplicate records (same email on multiple Contact rows), flag contacts with missing or invalid email addresses (which cannot migrate to Mailchimp), and inventory all active Power Automate flows tied to Contact and Lead entities. We pair this with a Mailchimp audience audit to identify existing members and groups that may conflict with incoming Dynamics 365 records. The discovery output is a written migration scope with record counts, data quality findings, and a list of excluded objects requiring manual handoff.

Schema mapping and Mailchimp merge field creation

We create the field mapping document mapping each Dynamics 365 Contact field (standard and custom) to a Mailchimp merge field or tag. We identify any Dynamics 365 fields that cannot map (lookups to other CRM entities, multi-select picklists exceeding Mailchimp type constraints) and document them as excluded or propose an equivalent tag strategy. The customer creates the required merge fields in Mailchimp during this window before we proceed to extraction. We also configure the Mailchimp Audience settings including default opt-in status and tag naming convention.

Data extraction from Dynamics 365 via Dataverse Web API

We extract Contacts and Leads from Dynamics 365 using the Dataverse Web API with batch pagination (500 records per page). For each record we extract emailaddress1, fullname, telephone1, address1 composite fields, parentaccountid lookup, ownerid, and all active custom field values. We run the extraction against the production environment during a designated read window (we do not require write lock during extraction). The extraction output is a staged CSV with all required fields plus a __source_system = d365 flag for audit.

Data transformation and deduplication

We transform the extracted data: we lowercase and trim all email addresses, run an MD5 hash for the Mailchimp member key, merge Lead and Contact records into a single audience member list, and apply the field-to-merge-field mapping. We run a deduplication pass: contacts sharing the same email address are consolidated with a preference for the most recently modified record or the record with the most complete field population. We flag unresolved duplicates for customer review. We also validate email address format and remove records with invalid email formats from the migration set (these are listed separately for the customer's admin to correct).

Pilot import and reconciliation

We run a pilot import of 100-200 records into the live Mailchimp audience to validate the merge field mapping, verify tag application, confirm opt-in status handling, and confirm that no record exceeds Mailchimp's character limits on text merge fields. The customer's admin reviews the Mailchimp audience in the UI to confirm data appearance and segmentation before we proceed to full import. Any mapping corrections happen here.

Full import via Mailchimp Marketing API

We run the full production import using the Mailchimp Marketing API with batch sizes of 80 members per request, respecting the 100-member limit. We apply Owner tags, Account group memberships, and any custom tag strategy defined during scoping. Each batch receives a retry with exponential backoff on 429 throttling responses. We log every failed record with the API error response for the customer's admin to correct and re-submit. We emit a final reconciliation report comparing the Dynamics 365 contact count against the Mailchimp member count and listing any unresolved duplicates or validation failures.

Cutover and handoff documentation

We deliver the full handoff package: the excluded-object inventory (Opportunities, Leads, Quotes, Orders, Invoices, Activities, Power Automate flows, Reports), the merge field mapping document, the data quality report listing invalid emails and unresolved duplicates, and the automation rebuild guide for Power Automate flows that need to become Mailchimp customer journeys. We do not rebuild Power Automate flows or configure Mailchimp automations as part of the migration scope; these are separate engagements. We support a three-day post-migration window for data corrections identified after cutover.