If there are duplicate contacts in your old platform(s), they will be merged into one contact during the migration process to ActiveCampaign.
We use the email address field as the merge field for each contact we migrate. The email address is the only unique identifier and required field in ActiveCampaign. This means that any duplicate email address and contact information from your previous system will automatically merge and overwrite existing fields during the migration process.
If there is a list or platform that has more up-to-date contact information, we recommend importing this last. Doing so ensures that any existing data will be overwritten with current information.