Mailchimp's SMS API is still in Beta, and several key features that integrations like ours depend on are not yet available. While you can technically map a Salesforce phone field to a Mailchimp SMS merge field, there are significant restrictions you should understand before setting this up.

The Solution

You can map to a Mailchimp SMS field, but the SMS phone number behaves as a write-once field in Mailchimp's Beta API. Field mappings will send an SMS phone number to Mailchimp when a contact is added to an audience for the first time, or when updating a contact that doesn't yet have an SMS number. Once an SMS phone number has been written to a contact, it cannot be changed or updated through the API. Your Mailchimp account must have SMS features enabled for this to work.

What SMS Mapping Cannot Do

Because Mailchimp's SMS API is still in Beta, several capabilities that exist for email are not yet available for SMS:

• SMS phone numbers are write-once. You can add an SMS phone number to a contact that doesn't have one, but once set, the Mailchimp API does not allow you to change or remove it. If someone changes their phone number in Salesforce, that update will not sync to Mailchimp. This is a known limitation of the Beta API.
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• No bulk imports. The API does not support bulk operations for SMS fields, so you cannot use the Data Wizard to import or update SMS numbers.
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• No SMS activity or engagement data. There are currently no API endpoints for SMS delivery status, click tracking, or engagement data. The email activity endpoints do not include SMS data, so the integration cannot pull back SMS reporting into Salesforce, even though these reports are visible in the Mailchimp web UI.
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• SMS-only contacts are not visible via the standard API. Contacts created through the SMS Beta API that have no email address do not appear through Mailchimp's traditional members endpoint, which our integration relies on for sync and reporting.

What We're Watching For

Mailchimp's SMS API is actively being developed. We have provided detailed feedback to Mailchimp on these limitations and will update our integration as new SMS capabilities become available.