Hi,

I am currently evaluating using libcurl in the openchange project
(http://www.openchange.org, an implementation of the Microsoft Exchange RPC
protocols) for both HTTP and SMTP transfers. HTTP looked OK.

However I wasn't able to find an SMTP example, which is a bit unfortunate.

I've developed a (very) simple example of using libcurl to send SMTP - see
attached patch.

I'd appreciate any review comments on this, to improve both the example and my
understanding of libcurl. To assist, I've inlined the source code as well.

Brad

#include <stdio.h>
#include <string.h>
#include <curl/curl.h>

int main(void)
{
  CURL *curl;
  CURLcode res;
  struct curl_slist *recipients = NULL;
  
  /* this becomes the Return-Path header value */
  static const char *from = "bradh_at_exmaple.com";
  
  /* this becomes the Envelope-to header value */
  static const char *to = "bradh_at_example.net";

  curl = curl_easy_init();
  if(curl) {
    /* this is the URL for your mailserver - you can also use an smtps:// URL here */
    curl_easy_setopt(curl, CURLOPT_URL, "smtp://mail.example.net.");
    
    /* Note that this option isn't strictly required, omitting it will result in libcurl
     * will sent the MAIL FROM command with no sender data. That may result in the
     * receiving SMTP system rewriting the header, which will look a bit strange. */
    curl_easy_setopt(curl, CURLOPT_MAIL_FROM, from);
    
    /* Note that the CURLOPT_MAIL_RCPT takes a list, not a char array */
    recipients = curl_slist_append(recipients, to);
    /* You really do have to set this option though - libcurl won't work without it */
    curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, recipients);

    /* You provide the remaining headers (including To:, Cc:, Bcc: and From:) and
     * the body of the message as the "data" element. There are two choices - either
     * provide a callback function and specify the function name using the
     * CURLOPT_READFUNCTION option; or just provide a FILE pointer that can be used
     * to read the data from. The easiest case is just to read from standard input,
     * (which is available as a FILE pointer) as shown here.
     */
    curl_easy_setopt(curl, CURLOPT_READDATA, stdin);

    /* send the message (including headers) */
    res = curl_easy_perform(curl);

    /* free the list of recipients */
    curl_slist_free_all(recipients);
    
    /* curl won't send the QUIT command until you call cleanup, so you should be able
     * to re-use this connection for additional messages (setting CURLOPT_MAIL_FROM and
     * CURLOPT_MAIL_RCPT as required, and calling curl_easy_perform() again. It may not
     * be a good idea to keep the connection open for a very long time though, and
     * you do want to clean up in the end.
     */
    curl_easy_cleanup(curl);
  }
  return 0;
}

-------------------------------------------------------------------
List admin: http://cool.haxx.se/list/listinfo/curl-library
Etiquette: http://curl.haxx.se/mail/etiquette.html