Sending Attachments with Templates
For sending attachments with templates you have a few different options:
When sending messages using the SparkPost REST API, the message body can be specified either “inline” as part of the transmission request or by referring to a stored template. When using an inline template, you can specify attachments to include in the final message through the content.attachments attribute. However, when using a stored template, the content.attachments attribute is not available.
If you have a fixed attachment to include within a stored template, you can embed it within the template by populating the template’s email_rfc822 attribute with a preformed multipart message. In this context, a fixed attachment is one which is the same for all deliveries and recipients.