Not sure how many people here are familiar with constant contact (http://www.constantcontact.com/). Giving a link would be more helpful.
There seem to be many 3rd party solutions available for integration with different CRM systems available in market. Also there should be some standard APIs exposed by constant-contact using which custom solutions could be developed for your requirement.
If you reach out to them, they probably would answer this question better.
- Arvind