Mailchimp Multilingual Campaigns

What this skill covers

Campaign- and audience-level patterns for sending multilingual emails through Mailchimp. Two distinct shapes:

1. Single list, multiple languages — one audience whose members speak different languages. The Belgian (NL/FR/DE), Swiss (DE/FR/IT/RM), Canadian (EN/FR), and Singaporean (EN/ZH/MS/TA) case. Use Mailchimp's audience-level MC_LANGUAGE field plus conditional content (or segment routing).
2. Global brand, multiple markets — separate audiences per market, sometimes separate Mailchimp accounts. Template syndication / forking workflow, per-market regulatory footers, multi-account orchestration. Bigger-org territory.

Template-level concerns are handled by the sibling skill mailchimp-template-language. That covers the lang attribute, character coverage, per-script font stacks, RTL layout, and everything inside a single template file. This skill adds the audience and campaign layer on top.

When to use this skill

Trigger this skill when:

• The user is sending a campaign to subscribers who speak different languages.
• The user asks about *|MC_LANGUAGE|*, *|IF:MC_LANGUAGE=...|*, language segments, or per-language content blocks.
• The user is planning a multi-market send across separate audiences or Mailchimp accounts.
• The user asks "should I send one campaign with conditional content, or one campaign per language?"
• The user is in Belgium / Switzerland / Canada / Singapore / Luxembourg / South Africa / India / any market with multiple official languages and is sending email to all of them.

Do not use this skill for:

• A single-language Mailchimp template — load mailchimp-template-language directly.
• Generic web/app i18n (not Mailchimp).
• Professional translation workflow tooling (this skill orchestrates Mailchimp's built-ins; it doesn't translate text).

The three documented paths

Mailchimp's own contact-languages doc (https://mailchimp.com/help/view-and-edit-contact-languages/) lists three sanctioned approaches for serving content in multiple languages. None is universally best — pick based on constraints.

The bright line: Mailchimp explicitly states "It's not possible to translate the subject line of your email." If the subject line must differ per language, you're on the segments path. There's no workaround.

Hard rules

Things that will silently break a multilingual campaign:

• *|MC_LANGUAGE|* returns an ISO 639-1 code like en, fr, nl, de. Mailchimp accepts a small set of locale variants too: fr_CA, es_ES, pt_PT. Most variants you might expect — de_CH, it_CH, rm, zh_Hant — are not in Mailchimp's accepted list and collapse to the base code (or are absent entirely). See references/language-detection.md for the full accepted list.
• Conditional comparisons are case-sensitive. *|IF:MC_LANGUAGE=fr|* matches; *|IF:MC_LANGUAGE=FR|* does not. Use lowercase to match the ISO codes Mailchimp stores.
• Always provide a *|ELSE:|* fallback. New subscribers default to "Not yet detected" until Mailchimp's auto-detection runs (or the user sets a value manually). Without an ELSE branch, those recipients get an empty email body. The fallback is usually the brand's primary language.
• A conditional block must open and close within the same mc:edit region. Splitting *|IF:MC_LANGUAGE=fr|* across two editable regions silently breaks at send time. See mailchimp-template-language → references/merge-tags.md for the block-scope rule.
• Compliance footer must be present in every language version. Translate the text (Unsubscribe / Update preferences) but keep the merge tags as-is (*|UNSUB|*, *|HTML:LIST_ADDRESS_HTML|*). Address and unsubscribe link are not optional in any locale.
• Language preference is a system-level field, not a custom merge field. Don't try to set it via *|MERGE5|* or similar; use Mailchimp's built-in Language attribute (auto-detected from browser, exposed on signup forms, manageable via API and CSV import).

Workflow

When asked to plan or build a multilingual campaign, work through these phases. Each phase points to the reference file that owns the detail.

Phase 1 — Identify the shape

Single-list-multilingual (one audience, many languages) or multi-market-global-brand (multiple audiences, often multiple accounts)? Confirm with the user. The patterns and reference files differ.

For multi-market work, load references/multi-market.md.

For single-list-multilingual (the default and best-supported shape in Mailchimp), continue.

Phase 2 — Map the constraints

Ask the user — or infer from the brief:

1. Which languages? Get the list and the priority (which is the "primary" / fallback).
2. Must the subject line differ per language? If yes → segments path is forced. If no → conditional-content path is viable.
3. How is language preference captured today? Browser auto-detection (Mailchimp's default), signup-form field, CSV import, or unset on all contacts? If unset, the user needs to set it before sending matters.
4. Are there per-language regulatory differences? Different compliance footer text, currency, jurisdiction. Single-list-multilingual generally implies one jurisdiction (Belgium has one address); multi-market implies many.

Phase 3 — Choose the path

Load references/segments-vs-conditional.md to walk the decision tree and apply the choice to the user's constraints.

Phase 4 — Establish how language is captured

Load references/language-detection.md to confirm how MC_LANGUAGE gets populated and what values are allowed. If the user's audience has mostly "Not yet detected" contacts, this is the gate — language-aware sends only work once language is set on contacts.

Phase 5 — Build the template

Load mailchimp-template-language (the sibling skill) for the actual HTML scaffold, mc:edit placement, responsive structure, accessibility, and validation. This skill doesn't duplicate that work — it composes with it.

When the path requires conditional content blocks (single-campaign approach, or hybrid where some sections vary per language but the subject doesn't), load references/conditional-content.md for the *|IF:MC_LANGUAGE=...|* patterns: per-language hero, CTA, compliance footer, signature block.

Phase 6 — Validate

Two layers:

1. Structural: run mailchimp-template-language/scripts/validate.py on each template file. Same validator as the monolingual flow.
2. Multilingual completeness — manual checklist:
   • Every conditional block has an *|ELSE:|* fallback for "Not yet detected" contacts.
   • Every language's content path includes the compliance footer.
   • The lang attribute on <html> matches the dominant language of the template (for the segments path, set per-segment).
   • Font stacks cover every script the languages need (see `mailchimp-templa