Error 128 ("Recipient not found in list") occurs when the SendMailing API is called against an Acoustic Transact organization. This error appears even when the recipient email address exists in the database.
What causes this error
The SendMailing API is part of the Acoustic Campaign XML API suite and is designed for Campaign organizations only. It cannot be used with Transact organizations. When SendMailing is called against a Transact organization, the system attempts to locate recipients using Campaign-specific list and database logic. Because Transact organizations do not support this lookup method, the request fails and returns Error 128.
API compatibility
Acoustic Campaign and Acoustic Transact are separate products with different architectures, APIs, and delivery mechanisms:
- SendMailing API → Supported only in Acoustic Campaign
- Transact organizations → Do not support the SendMailing API
Calling Campaign APIs against a Transact organization will result in recipient lookup failures, even if the contact exists in the database.
The correct API for Transact organizations
If you are working with a Transact organization, use the XTMailing API instead. The XTMailing API is specifically built for transactional message delivery in Transact and uses a different request structure and processing flow than SendMailing.
Full documentation is available in the Acoustic Developer Portal under: Transact XML Overview → XTMailing API.
Dynamic content considerations
Dynamic content is implemented differently across the two platforms:
- Acoustic Campaign: Supports dynamic content rule sets that can be referenced directly in SendMailing API calls.
- Acoustic Transact: Uses message scripting where logic is embedded directly into email templates and content is conditionally rendered based on recipient data at send time.
If your use case relies on dynamic content, ensure your implementation aligns with the correct platform's approach.
How to identify your organization type
To confirm whether your organization is Campaign or Transact:
- Check your organization name in the Acoustic UI — Transact organizations typically include "TRANSACT" in the name.
- Contact Acoustic Support to verify your organization type.
Correctly identifying your organization type is essential for selecting the appropriate APIs and avoiding integration errors.