C send mail without authentication
The classic "send mail without authentication" question!
In C, you can send an email without authentication using the sendmail
command or the libcurl
library. Here are some examples:
Using sendmail
command:
#include <stdio.h>
#include <stdlib.h>
int main() {
FILE *fp = popen("sendmail -t -i -f [email protected] -c 'Subject: Test email' 'Hello, world!'","w");
if (fp == NULL) {
perror("popen");
return 1;
}
fclose(fp);
return 0;
}
This code uses the popen
function to execute the sendmail
command with the -t
option, which tells sendmail
to read the email message from standard input. The -i
option tells sendmail
to ignore the From
header, and the -f
option specifies the sender's email address. The -c
option specifies the subject, and the final string is the email body.
Using libcurl
library:
#include <curl/curl.h>
#include <stdio.h>
int main() {
CURL *curl;
CURLcode res;
curl_global_init(CURL_GLOBAL_DEFAULT);
curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "smtp://your_smtp_server:port");
curl_easy_setopt(curl, CURLOPT_MAIL_FROM, "[email protected]");
curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, "[email protected]");
curl_easy_setopt(curl, CURLOPT_READDATA, "Hello, world!");
curl_easy_setopt(curl, CURLOPT_READFUNCTION, NULL);
res = curl_easy_perform(curl);
if(res!= CURLE_OK) {
fprintf(stderr, "cURL error: %s\n", curl_easy_strerror(res));
}
curl_easy_cleanup(curl);
}
curl_global_cleanup();
return 0;
}
This code uses the libcurl
library to send an email without authentication. You'll need to replace your_smtp_server
and port
with your actual SMTP server and port. The CURLOPT_MAIL_FROM
and CURLOPT_MAIL_RCPT
options specify the sender's and recipient's email addresses, respectively. The CURLOPT_READDATA
option specifies the email body.
Please note that sending email without authentication is generally not recommended, as it can lead to spam and security issues. It's always a good idea to use authentication (e.g., using STARTTLS
or AUTH
) to ensure the integrity and security of your email communications.