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MailChimp vs. Mandrill | MailChimp.com: KB Article[
^] . MailChimp is a subscriber-based system.
You create lists in MailChimp and send campaigns to your confirmed subscribers. Our Terms of Use require you to get express permission from anyone you send to.
Mandrill is a recipient-based system.
Contact lists and other recipient information can't be stored in Mandrill. Instead, this data is managed in your own database or application, and passed to Mandrill in your API request or SMTP message when the transactional email is triggered.
Although Mandrill is accessed through your MailChimp account, it doesn't offer the same tools and features as MailChimp.