The company has finally implemented attachments in their JSON-based REST API, which was previously lacking this feature. The developers used base64-encoded strings to make the data more resilient to encoding problems. The API is fully backwards compatible and allows users to send one or more attachments with a maximum size of 10MB. However, sending large files or viruses is not allowed and requires special permission. The company plans to update their client libraries in the near future, including the Ruby library. It is recommended that apps send email with attachments from a background job to avoid issues with message size and submission time.