Migrate from Mailchimp Transactional to Mailtrap

Migration Checklist

1. Authenticate your domain
   Add and verify your domain before sending. Follow the Domain Setup article at docs.mailtrap.io.

2. Get your API token
   Mailtrap auto-generates a token when you add a domain. Find it under Settings → API Tokens. Read more on API tokens.
3. Update your integration
   Swap your Mailchimp Transactional endpoints and credentials for Mailtrap’s (API or SMTP). See the migration sections below.
4. Migrate templates
   Both platforms use Handlebars, so content migrates directly. See the templates sections below.
5. Migrate suppressions
   Export Mailchimp Transactional suppressions and import them into Mailtrap via CSV or manually. Click here for more information.
6. Migrate users
   Add users from the User Management tab and review permissions during migration.
7. Set up webhooks
   Follow the Mailtrap Webhooks step-by-step guide.
8. Security and compliance
   Visit the Trust Center page to review Mailtrap’s security practices and compliance standards.

Concepts

Sending domains

Mailchimp Transactional equivalent: Sending Domains / Domain Authentication

Both platforms require DNS-based domain authentication using SPF, DKIM, and DMARC records. Mailchimp uses two CNAME records for DKIM, plus a TXT record for domain ownership verification. Mailtrap also requires DMARC validation. 

The DNS standards are the same. The difference is in how each platform surfaces domain status and what records it generates for you.

And DKIM records can be added alongside Mailchimp’s (different selectors, no conflict), and one DMARC record covers both. 

Important: For Mailchimp specifically, SPF inclusion (servers.mcsv.net) is optional. DMARC compliance is achieved via DKIM alone, since Mailchimp doesn’t use your domain in the Return-Path. Adding it to your SPF record is technically harmless but increases your DNS lookup count unnecessarily.

See the Mailtrap domain setup guide for step-by-step instructions.

Separate sending streams

Mailchimp Transactional equivalent: N/A – single endpoint

Mailchimp routes all email through a single API endpoint and SMTP host. Mailtrap separates transactional and bulk email into distinct infrastructure:

• Transactional: For sending user-triggered emails like welcome emails and password resets.
• Bulk: For sending promotional, marketing, emails like newsletters and product updates.

By keeping the sending infrastructures separate, you are able to:

• Protect your transactional email reputation from the performance of your bulk campaigns
• Ensure each stream routes through the right IP pools
• Give mailbox providers the signals they need to categorize and deliver your emails correctly

Email categories

Mailchimp Transactional equivalent: Tags (up to 100 per message)

Mailchimp uses tags – an array of strings in the API request – to group messages for stats aggregation. Stats accumulate per-tag, and you can filter activity by tag.

Mailtrap uses Email Categories – set via the category field in the API or the X-MT-Category header in SMTP. Categories serve a similar purpose: grouping messages for tracking and analytics.

Key difference: Mailchimp supports multiple tags per message; Mailtrap assigns one category per message.

Organization & sub-accounts

Mailchimp Transactional equivalent: Subaccounts

Mailchimp’s Subaccounts API lets you segment sending reputation, track stats, and manage quotas per tenant or team. You pass a subaccount ID in the send request.

Mailtrap offers Organization and sub-account management from Business plan onwards. It lets you manage complex setups involving multiple teams, clients, environments, or products under a single Organization. To start using the feature, you first need to enable it under the Organization tab.

Terminology comparison

API migration

Authentication

Mailchimp Transactional and Mailtrap authenticate differently:

Mailchimp’s approach means the API key travels inside the payload, not the header. When migrating, move your auth from the request body to the Authorization header.

API mapping

Outbound Sending API JSON Field Mapping

Code snippets

Note: Mailchimp Transactional nests all message fields inside a “message” object with the API key at the top level. Mailtrap uses a flat structure with auth in the header.

SMTP migration

Migration notes:

• Host: Replace smtp.mandrillapp.com with the appropriate Mailtrap host. If you send both transactional and bulk email over SMTP, you now need two separate SMTP configurations.
• Username: Mailchimp Transactional accepts any email address as the username (it’s ignored for auth). Mailtrap requires the literal string api.
• Port 465: Mailchimp supports implicit TLS on port 465. Mailtrap does not – use port 587 with STARTTLS instead.
• Password: Both use an API key/token as the password. Generate a new token in your Mailtrap dashboard.

For more information on migrating your SMTP configuration, click this link. ⬅️

Rate limits & quotas

Email templates

Mailchimp Transactional supports two template syntaxes: Mailchimp merge tags (*|VAR|*) and Handlebars ({{var}}). Mailtrap uses Handlebars exclusively.

If your Mailchimp templates already use Handlebars (merge_language: "handlebars"), the template markup migrates directly – just copy the HTML.

Syntax comparison

Migration notes: 

• Mailchimp Transactional variable format uses arrays of {“name“: “var“, “content”: “value“} objects, with separate global_merge_vars (all recipients) and merge_vars (per-recipient). 
• Mailtrap uses a flat template_variables object: {“var“: “value“}. You’ll need to restructure this when migrating your send calls.