smtp-mime.c
/*************************************************************************** * _ _ ____ _ * Project ___| | | | _ \| | * / __| | | | |_) | | * | (__| |_| | _ <| |___ * \___|\___/|_| \_\_____| * * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. * * This software is licensed as described in the file COPYING, which * you should have received as part of this distribution. The terms * are also available at https://curl.se/docs/copyright.html. * * You may opt to use, copy, modify, merge, publish, distribute and/or sell * copies of the Software, and permit persons to whom the Software is * furnished to do so, under the terms of the COPYING file. * * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY * KIND, either express or implied. * * SPDX-License-Identifier: curl * ***************************************************************************/ /* <DESC> * Send SMTP mime emails * </DESC> */ #include <stdio.h> #include <string.h> #include <curl/curl.h> /* This is a simple example showing how to send mime mail using libcurl's SMTP * capabilities. For an example of using the multi interface please see * smtp-multi.c. * * Note that this example requires libcurl 7.56.0 or above. */ #define FROM "<sender@example.org>" #define TO "<addressee@example.net>" #define CC "<info@example.org>" static const char *headers_text[] = { "Date: Tue, 22 Aug 2017 14:08:43 +0100", "To: " TO, "From: " FROM " (Example User)", "Cc: " CC " (Another example User)", "Message-ID: <dcd7cb36-11db-487a-9f3a-e652a9458efd@" "rfcpedant.example.org>", "Subject: example sending a MIME-formatted message", NULL }; static const char inline_text[] = "This is the inline text message of the email.\r\n" "\r\n" " It could be a lot of lines that would be displayed in an email\r\n" "viewer that is not able to handle HTML.\r\n"; static const char inline_html[] = "<html><body>\r\n" "<p>This is the inline <b>HTML</b> message of the email.</p>" "<br />\r\n" "<p>It could be a lot of HTML data that would be displayed by " "email viewers able to handle HTML.</p>" "</body></html>\r\n"; int main(void) { CURL *curl; CURLcode result = curl_global_init(CURL_GLOBAL_ALL); if(result != CURLE_OK) return (int)result; curl = curl_easy_init(); if(curl) { struct curl_slist *headers = NULL; struct curl_slist *recipients = NULL; struct curl_slist *slist = NULL; curl_mime *mime; curl_mime *alt; curl_mimepart *part; const char **cpp; /* This is the URL for your mailserver */ curl_easy_setopt(curl, CURLOPT_URL, "smtp://mail.example.com"); /* Note that this option is not strictly required, omitting it results in * libcurl sending the MAIL FROM command with empty sender data. All * autoresponses should have an empty reverse-path, and should be directed * to the address in the reverse-path which triggered them. Otherwise, * they could cause an endless loop. See RFC 5321 Section 4.5.5 for more * details. */ curl_easy_setopt(curl, CURLOPT_MAIL_FROM, FROM); /* Add two recipients, in this particular case they correspond to the * To: and Cc: addressees in the header, but they could be any kind of * recipient. */ recipients = curl_slist_append(recipients, TO); recipients = curl_slist_append(recipients, CC); curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, recipients); /* allow one of the recipients to fail and still consider it okay */ curl_easy_setopt(curl, CURLOPT_MAIL_RCPT_ALLOWFAILS, 1L); /* Build and set the message header list. */ for(cpp = headers_text; *cpp; cpp++) headers = curl_slist_append(headers, *cpp); curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers); /* Build the mime message. */ mime = curl_mime_init(curl); /* The inline part is an alternative proposing the html and the text versions of the email. */ alt = curl_mime_init(curl); /* HTML message. */ part = curl_mime_addpart(alt); curl_mime_data(part, inline_html, CURL_ZERO_TERMINATED); curl_mime_type(part, "text/html"); /* Text message. */ part = curl_mime_addpart(alt); curl_mime_data(part, inline_text, CURL_ZERO_TERMINATED); /* Create the inline part. */ part = curl_mime_addpart(mime); curl_mime_subparts(part, alt); curl_mime_type(part, "multipart/alternative"); slist = curl_slist_append(NULL, "Content-Disposition: inline"); curl_mime_headers(part, slist, 1); /* Add the current source program as an attachment. */ part = curl_mime_addpart(mime); curl_mime_filedata(part, "smtp-mime.c"); curl_easy_setopt(curl, CURLOPT_MIMEPOST, mime); /* Send the message */ result = curl_easy_perform(curl); /* Check for errors */ if(result != CURLE_OK) fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(result)); /* Free lists. */ curl_slist_free_all(recipients); curl_slist_free_all(headers); /* curl does not send the QUIT command until you call cleanup, so you * should be able to reuse 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 long time though (more than a few minutes may * result in the server timing out the connection), and you do want to * clean up in the end. */ curl_easy_cleanup(curl); /* Free multipart message. */ curl_mime_free(mime); } curl_global_cleanup(); return (int)result; }
Notice
This source code example is simplified and may ignore return
codes and error checks. We do this to highlight the libcurl function calls and
related options and reduce unrelated code.
A real-world application does of course properly check every return value and exit correctly at the first serious error.