This API used to upload attachments in zixflow platform. Purpose of API is whenever the user wants to send an attachment in the email. user need to upload attachment in zixflow platform first. zixflow will provide id represents to attachment. and the user can send this id in send email API’s attachment field to send attachment along with the email
The “File” field refers to an attachment file that must be included in an
email campaign. The file can be in any format, and its size should not exceed
25 megabytes (MB).