The attachment parameters are not required unless you want to attach a document. Attachment parameters have a form of parameter_n. The letter “n” has to be replaced by a document index (starting with 0). Example:
- You must start with 0, or no attachment will be added.
- If you skip a number, e.g., 0, 1, 3, 4, only attachment 0 and 1 will be sent.