Mailchimp V2

Mailchimp is the most recognized name in SMB email marketing — large template library, audience management, automation workflows, and a solid REST API. Two separate products: Mailchimp Marketing API (for lists, campaigns, subscribers, templates) and Mandrill (transactional email, separate product and API key). For agents: manage subscriber lists, add/update members with tags and merge fields, create and schedule campaigns, and send transactional emails via Mandrill. Free tier (500 contacts, 1000 emails/month) covers early-stage use. Confidence is docs-derived.

Marketing API at {dc}.api.mailchimp.com/3.0 (dc = datacenter from API key). GET /lists lists audiences. POST /lists/{id}/members adds a subscriber ({email_address, status: subscribed/pending, merge_fields: {FNAME, LNAME}}). PUT /lists/{id}/members/{subscriber_hash} creates or updates a subscriber (subscriber_hash = MD5(lowercase_email)). PATCH /lists/{id}/members/{subscriber_hash} updates subscriber fields. GET /lists/{id}/members lists subscribers. POST /campaigns creates a campaign ({type, recipients: {list_id}, settings: {subject_line, from_name, reply_to}}). POST /campaigns/{id}/actions/send sends a campaign. Mandrill API (transactional): POST https://mandrillapp.com/api/1.0/messages/send ({key, message: {to, from_email, subject, html}}).

Marketing API: Basic auth (any_string:api_key). API keys from Mailchimp Account → Extras → API Keys. Account-scoped. HTTPS enforced. Datacenter prefix: API key ends in -{dc} (e.g., us1) — use in base URL. Mandrill: separate API key from Mandrill settings. OAuth2 for building Mailchimp Connected Apps. Subscriber hash: MD5 hash of lowercased email — required for per-member operations. Key rotation via UI.

Standard HTTP status codes with JSON error bodies ({title, status, detail, errors}). 400 for invalid email format or duplicate member (already subscribed). 404 for unknown list ID. Subscriber status: subscribed/unsubscribed/cleaned/pending/transactional — only subscribed status receives campaigns. Datacenter prefix in URL is a common integration bug. Rate limiting: 10 concurrent connections; no per-second hard limit. Mailchimp uptime at status.mailchimp.com. Mandrill is a separate service with its own SLA and rate limits.

mailchimp.com/developer covers Marketing API reference, Mandrill API reference, OAuth guide, and code samples. Getting started: create Mailchimp account (free), get API key and datacenter prefix, first subscriber add in under 10 minutes. No official SDK — community libraries exist for Python and Node.js. Interactive API playground in developer portal. Community via Mailchimp developer forum. Documentation is thorough; datacenter-prefixed URLs and subscriber hashing are the main quirks.