zoho-inputstream Input does not match the given pattern

zoho-inputstream Input does not match the given pattern

I'm trying to send an email by using cURL to communicate with the API.  Here's my request where the ZOHO_USER_ID is associated with the SYSTEM_ADDRESS email:
  1. curl -X POST "https://mail.zoho.com/api/accounts/$ZOHO_USER_ID/messages" -H "Authorization:Zoho-oauthtoken $PREVIOUSLY_RECEIVED_ACCESS_TOKEN" -H 'Content-Type: application/json' -d '{"fromAddress":"$SYSTEM_ADDRESS","toAddress":"$TEST_ADDRESS","subject":"Email - Always and Forever","content":"Email can never be dead. The most neutral and effective way, that can be used for one to many and two way communication."}'