Zoho send mail with attachments. Unable to send attachments

Zoho send mail with attachments. Unable to send attachments

Hi,
I am unable to send /  view attachments using zoho mail API.
These are the postman calls I made to upload an attachment and send mail

UPLOAD
Request  
url: " https://mail.zoho.com/api/accounts/xxxxxxxxxxxxxxxxxxx/messages/attachments?fileName=C:/node/latestioc/ioc/ioc-backend/simdata.xlsx"
headers: {"Authorization": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"}

Response
{
  "status": {
    "code": 200,
    "description": "success"
  },
  "data": {
    "storeName": "xxxxxxxxx",
    "attachmentName": "C:/node/latestioc/ioc/ioc-backend/simdata.xlsx",
    "attachmentPath": "/Mail/xxxxxxxxxxxxxxxxxxxxxxxxxx_xxxxxxxxxx-simdata.xlsx"
  }
}

SEND MAIL
Request
url: "https://mail.zoho.com/api/accounts/xxxxxxxxxxxxxxxxxxx/messages"
headers: {"Authorization": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx", "Content-Type": "application/json"}
body: 
{
"fromAddress": " xxxx@domain.io",
"toAddress": " yyyy@domain.com",
"subject": "Hello",
"content": "Email can never be dead. The most neutral and effective way, that can be used for one to many and two way communication.",
"attachments": [{"storeName": "xxxxxxxxx",
"attachmentPath": "/Mail/xxxxxxxxxxxxxxxxxxxxxxxxxx_xxxxxxxxxx-simdata.xlsx",
"attachmentName": "xxxxxxxxxxxxxxxxxxxxxxxxxx_xxxxxxxxxx-simdata.xlsx"
   }]
}

Response
{
  "status": {
    "code": 200,
    "description": "success"
  },
  "data": {
    "attachments": [
      {
        "attachmentName": "xxxxxxxxxxxxxxxxxxxxxxxxxx_xxxxxxxxxx-simdata.xlsx",
        "storeName": "xxxxxxxxx",
        "attachmentPath": "/Mail/xxxxxxxxxxxxxxxxxxxxxxxxxx_xxxxxxxxxx-simdata.xlsx"
      }
    ],
    "subject": "Hello",
    "fromAddress": " xxxx@domain.io",
    "toAddress": " yyyy@domain.com",
    "content": "Email can never be dead. The most neutral and effective way, that can be used for one to many and two way communication."
  }
}

I got the mail in gmail. When I tried to open the attachment in google sheets it shows error: " Unable to convert document.". I tried to open it in excel app, it says: "File format or file extension is not valid. verify that the file has not been corrupted and that the file extension matches the format of the file.". 
For upload header, I tried content-Type as application/x-www-form-urlencoded, application/json, application/octet-stream. Using x-www-form-urlencoded & json, I couldn't even send the email. Using octet-stream, I could send the email but the above problem prevails.
When I send the mail to zoho mail. I cannot even see the attachment. Someone please tell me what I'm doing wrong!