Sending authentication email question

To clarify; do you have to be hosting your app at a domain to use the email function ? I getting this error

POST
scheme https
host q1oclm9r8ql7.grandmoralis.com:2053
filename /server/functions/sendWelcomeEmail
Address [2606:4700:20::ac43:454c]:2053

Status

400

Bad Request

VersionHTTP/2

Transferred1.25 KB (61 B size)

Referrer Policystrict-origin-when-cross-origin

access-control-allow-headers X-Parse-Master-Key, X-Parse-REST-API-Key, X-Parse-Javascript-Key, X-Parse-Application-Id, X-Parse-Client-Version, X-Parse-Session-Token, X-Requested-With, X-Parse-Revocable-Session, X-Parse-Request-Id, Content-Type, Pragma, Cache-Control, X-Parse-Installation-Id
access-control-allow-methods GET,PUT,POST,DELETE,OPTIONS
access-control-allow-origin *
access-control-expose-headers X-Parse-Job-Status-Id, X-Parse-Push-Status-Id
cf-cache-status DYNAMIC
cf-ray 69e0b616bf0552c5-LAX

etc
but it may be because I am running only local host app