Mailchimp – Set Different Reply-To Address from From Address

It appears that method 3 is a valid solution if you have some programming skills.

I contacted the MailChimp and Mandrill support and they both confirmed that it's possible to send newsletters with Mandrill. MailChimp even allows you to use pre-defined templates for your Mandrill newsletter.

The solution is to write a script (in a language like Ruby or JavaScript with Node.js) that will send emails to a list of addresses (it's possible to export your entire list as a CSV file in Mailchimp) in batches of 100 or so with a small time interval between each batch.

To handle unsubscriptions, you can use Mandrill's UNSUB merge tag together with the Webhooks feature. You can set up a web service that will receive POST requests from Mandrill whenever an unsubscription happens (e.g. you can set it up to POST to http://mysite.com/unsubscribe). Your web service will then have to use the Mailchimp API to unsubscribe the address communicated by Mandrill from your list.

Although this solution can be laborious or hard to do if you don't know where to start, it can save you hundreds of dollars and can be a valid way if you have the skills required.

If you just unsubscribe that user, the user can re-subscribe again and receive your emails. I suggest creating a new segment called "Blacklisted" or similar and add unwanted users to that segment (not list, but segment). When you want to send a new email blast you can set to send it to all users except for the Segment name "Blacklisted".