We are immersed in Integrating a Drupal ecommerce site with the Mailchimp Newsletter management system.
Some of this work is identifying, installing and configuring existing Drupal modules. Some of the work is extending the code to cater for specific purpose. And a large proportion of the work is testing, verifying and tuning the customer workflow.
The result will be that the Ubercart customer database will be available in Mailchimp, for sending out campaign newsletters, and Mailchimp will handle stuff like allowing people to unsubscribe.
Optionally, the Drupal content can be made available into a Mailchimp campaign.
Contact us for a quote for similar work on your Drupal 7 Ubercart site. Or an estimate on other versions of Drupal and/or other Drupal ecommerce suites.