How to check if mail servers found in c

To check if mail servers are found in C, you can use the following steps:

Use the gethostbyname() function: This function returns a pointer to a hostent structure that contains information about the host, including the mail server(s) associated with it.

Here's an example code snippet:

#include <stdio.h>
#include <netdb.h>

int main() {
    struct hostent *he;
    char *hostname = "example.com"; // replace with the domain name you want to check

    he = gethostbyname(hostname);
    if (he == NULL) {
        printf("Error: %s\n", hstrerror(h_errno));
        return 1;
    }

    printf("Mail servers for %s:\n", hostname);
    for (struct mailaddr *ma = he->h_aliases; ma!= NULL; ma = ma->ma_next) {
        printf("%s\n", ma->ma_name);
    }

    return 0;
}

In this example, we use the gethostbyname() function to retrieve the hostent structure for the specified hostname. We then iterate through the h_aliases field of the hostent structure, which contains an array of mail server names.

Use the getaddrinfo() function: This function returns a pointer to a struct addrinfo structure that contains information about the host, including the mail server(s) associated with it.

Here's an example code snippet:

#include <stdio.h>
#include <sys/socket.h>
#include <netdb.h>

int main() {
    struct addrinfo hints, *res;
    char *hostname = "example.com"; // replace with the domain name you want to check

    memset(&hints, 0, sizeof(hints));
    hints.ai_family = AF_INET; // or AF_INET6 for IPv6
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;

    getaddrinfo(hostname, NULL, &hints, &res);
    if (res == NULL) {
        printf("Error: %s\n", gai_strerror(errno));
        return 1;
    }

    printf("Mail servers for %s:\n", hostname);
    for (struct addrinfo *ai = res; ai!= NULL; ai = ai->ai_next) {
        for (struct mailaddr *ma = ai->ai_aliases; ma!= NULL; ma = ma->ma_next) {
            printf("%s\n", ma->ma_name);
        }
    }

    freeaddrinfo(res);
    return 0;
}

In this example, we use the getaddrinfo() function to retrieve the addrinfo structure for the specified hostname. We then iterate through the ai_aliases field of the addrinfo structure, which contains an array of mail server names.

Note that these examples assume that the mail server names are stored in the DNS records associated with the hostname. If the mail server names are not stored in the DNS records, these examples will not work.

Mail Knowledge

How to check if mail servers found in c