Not being notified in Mailchimp when subscribers are added via Zapier

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 want to include the time your Zap runs in your Zap (or use that as an approximation of when the trigger occurs), you can use the following field in your Zap: {{zap_meta_human_now}}

Just enter that text with the curly braces into the field instead of selecting something from the dropdown.

For more information, see: https://zapier.com/help/advanced-tips/#time-stamps