The Edge can directly upload your customer mailing lists for use in Constant Contact. Once uploaded, the mailing lists will remain synchronized between the two platforms, meaning adding or removing customers from the list will transfer this change.
This requires an active account with them and is subject to their terms, conditions, and pricing. Please note that pricing is based on the number of contacts and number of emails sent.
For more information: https://www.constantcontact.com/pricing
Visit the Authenticate Constant Contact article for step-by-step instructions on linking your Constant Contact account with Edge for uploading.