C语言发送邮件 基于libesmtp库

其他方法：（基于libesmtp库）

1、安装库libesmtp-devel

yum install libesmtp-devel
或
apt-get install libesmtp-devel

如果没法用命令安装，就上http://www.stafford.uklinux.net/libesmtp/自己下载包安装。

2、不认证即可发信息

#define _XOPEN_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <unistd.h>
#include <getopt.h>
#include <string.h>
#include <fcntl.h>
#include <signal.h>
#include <errno.h>
#include <stdarg.h>
#include <libesmtp.h>

int main() {
smtp_session_t session;
smtp_message_t message;
struct sigaction sa;
const smtp_status_t *status;
char buf[128];
FILE *fp;
/* This program sends only one message at a time. Create an SMTP
session and add a message to it. */
if( (session = smtp_create_session ()) == NULL){
fprintf (stderr, "smtp_create_session problem %s\n",
smtp_strerror (smtp_errno (), buf, sizeof buf));
return 1;
}
if((message = smtp_add_message (session)) == NULL){
fprintf (stderr, "smtp_add_message problem %s\n",
smtp_strerror (smtp_errno (), buf, sizeof buf));
return 1;
}
/* NB. libESMTP sets timeouts as it progresses through the protocol.
In addition the remote server might close its socket on a timeout.
Consequently libESMTP may sometimes try to write to a socket with
no reader. Ignore SIGPIPE, then the program doesn't get killed
if/when this happens. */
sa.sa_handler = SIG_IGN;
sigemptyset (&sa.sa_mask);
sa.sa_flags = 0;
sigaction (SIGPIPE, &sa, NULL);
/* Set the host running the SMTP server. LibESMTP has a default port
number of 587, however this is not widely deployed so the port
is specified as 25 along with the default MTA host. */
smtp_set_server (session, "127.0.0.1:25");
/* Set the reverse path for the mail envelope. (NULL is ok)
*/
smtp_set_reverse_path (message, "test@test.com");
/* RFC 2822 doesn't require recipient headers but a To: header would
* be nice to have if not present. */
smtp_set_header (message, "To", NULL, NULL);
smtp_set_header (message, "Subject", " test mail");
smtp_set_header_option (message, "Subject", Hdr_OVERRIDE, 1);
fprintf(stderr,"%s\n","smtp_set_server.");
if ((fp = fopen ("test-mail.eml", "r")) == NULL) {
fprintf (stderr, "can't open mail file: %s\n", strerror (errno));
return (1);
}
smtp_set_message_fp (message, fp);
smtp_add_recipient (message,"yourQQ@qq.com");
/* Initiate a connection to the SMTP server and transfer the
message. */
if (!smtp_start_session (session)){
fprintf (stderr, "SMTP server problem %s\n",
smtp_strerror (smtp_errno (), buf, sizeof buf));
}
else{
/* Report on the success or otherwise of the mail transfer.
*/
status = smtp_message_transfer_status (message);
printf ("%d %s", status->code,
(status->text != NULL) ? status->text : "\n");
}
/* Free resources consumed by the program.
*/
smtp_destroy_session (session);
if(fp != NULL){
fclose(fp);
}

return 0;
}

3、把上面的代码写入sendmail.c，并把里面的"yourQQ@qq.com"替换成你自己的QQ邮箱地址或者其它邮箱地址，然后用下面命令编译

gcc -std=c99 -Wall `libesmtp-config --cflags`   -o sendmail sendmail.c -lesmtp

4、同目录下新建test-mail.eml文件，里面内容随便自己填。

5、运行

./sendmail