CURLcode curl_easy_setopt(CURL *handle, CURLOPT_MAIL_FROM, char *from);
An originator email address should be specified with angled brackets (<>) around it, which if not specified will be added automatically.
If this parameter is not specified then an empty address will be sent to the mail server which may cause the email to be rejected.
The application does not have to keep the string around after setting this option.
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "smtp://example.com/");
curl_easy_setopt(curl, CURLOPT_MAIL_FROM, "president@example.com");
ret = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}