Thread: sending message to GMAIL using SMTP

Hi,
I was trying to send a message to my gmail account using a program I found on the web. I had to modify it and ask for help on a forum to get it to work. I was successfully receiving the emails and everything looked fine. Then after about 2 days, it stopped working. So I checked the log file and this is what it contained:

Connecting....
220 mx.google.com ESMTP l12si10852221fgb.8

helo me.somepalace.com
250 mx.google.com at your service

MAIL FROM:<[email protected]>
250 2.1.0 OK

RCPT TO:<[email protected]>
250 2.1.5 OK

DATA
354 Go ahead

To:[email protected]
From:[email protected]
Subject:Logged

.

550-5.7.1 [87.109.73.118] The IP you're using to send email is not authorized

550-5.7.1 to send email directly to our servers. Please use

550 5.7.1 the SMTP relay at your service provider instead. l12si10852221fgb.8

quit
221 2.0.0 mx.google.com closing connection l12si10852221fgb.8

Gmail is obviously not allowing me to send emails using my IP. But I don't know much about networking. All I know is how to setup my home network...
Is there any way to fix this?
Here's the code:

Code:

#define cmailserver "gmail-smtp-in.l.google.com"
#define cemailto "[email protected]"
#define cemailfrom "[email protected]"
#define SMTPLog "SMTP log.txt"
#define cemailsubject "test"
#define waittime 30

int MailIt(char *mailserver, char *emailto, char *emailfrom,
           char *emailsubject, char *emailmessage, long maxlen)
{
	SOCKET sockfd;
    WSADATA wsaData;
    FILE *smtpfile;

    #define bufsize 300
    int bytes_sent;   /* Sock FD */
    int err;
    struct hostent *host;   /* info from gethostbyname */
    struct sockaddr_in dest_addr;   /* Host Address */
    char line[maxlen+100];
    char *Rec_Buf = (char*) malloc(bufsize+1);
    smtpfile=fopen(SMTPLog,"a+");
    if (WSAStartup(0x202,&wsaData) == SOCKET_ERROR)
	{
		fputs("WSAStartup failed",smtpfile);
		WSACleanup();
		return -1;
    }
    if ( (host=gethostbyname(mailserver)) == NULL)
	{
		perror("gethostbyname");
		exit(1);
    }
    memset(&dest_addr,0,sizeof(dest_addr));
    memcpy(&(dest_addr.sin_addr),host->h_addr,host->h_length);

	/* Prepare dest_addr */
	dest_addr.sin_family= host->h_addrtype;  /* AF_INET from gethostbyname */
	dest_addr.sin_port= htons(25); /* PORT defined above */

	/* Get socket */

	if ((sockfd=socket(AF_INET,SOCK_STREAM,0)) < 0)
	{
		perror("socket");
		exit(1);
	}
	/* Connect !*/
	fputs("Connecting....\n",smtpfile);

	if (connect(sockfd, (struct sockaddr *)&dest_addr,sizeof(dest_addr)) == -1)
	{
		perror("connect");
        exit(1);
	}
	Sleep(waittime);
	err=recv(sockfd,Rec_Buf,bufsize,0);Rec_Buf[err] = '\0';
	fputs(Rec_Buf,smtpfile);
	strcpy(line,"helo me.somepalace.com\n");
	fputs(line,smtpfile);
	bytes_sent=send(sockfd,line,strlen(line),0);
	Sleep(waittime);
	err=recv(sockfd,Rec_Buf,bufsize,0);Rec_Buf[err] = '\0';
	fputs(Rec_Buf,smtpfile);
	strcpy(line,"MAIL FROM:<");
	strncat(line,emailfrom,strlen(emailfrom));
	strncat(line,">\n",3);
	fputs(line,smtpfile);
	bytes_sent=send(sockfd,line,strlen(line),0);
	Sleep(waittime);
	err=recv(sockfd,Rec_Buf,bufsize,0);Rec_Buf[err] = '\0';
	fputs(Rec_Buf,smtpfile);
	strcpy(line,"RCPT TO:<");
	strncat(line,emailto,strlen(emailto));
	strncat(line,">\n",3);
	fputs(line,smtpfile);
	bytes_sent=send(sockfd,line,strlen(line),0);
	Sleep(waittime);
	err=recv(sockfd,Rec_Buf,bufsize,0);Rec_Buf[err] = '\0';
	fputs(Rec_Buf,smtpfile);
	strcpy(line,"DATA\n");
	fputs(line,smtpfile);
	bytes_sent=send(sockfd,line,strlen(line),0);
	Sleep(waittime);
	err=recv(sockfd,Rec_Buf,bufsize,0);Rec_Buf[err] = '\0';
	fputs(Rec_Buf,smtpfile);
	Sleep(waittime);
	strcpy(line,"To:");
	strcat(line,emailto);
	strcat(line,"\n");
	strcat(line,"From:");
	strcat(line,emailfrom);
	strcat(line,"\n");
	strcat(line,"Subject:");
	strcat(line,emailsubject);
	//strcat(line,"\n");
	//strcat(line,emailmessage);
	strcat(line,"\r\n.\r\n");
	fputs(line,smtpfile);
	bytes_sent=send(sockfd,line,strlen(line),0);
	Sleep(waittime);
	err=recv(sockfd,Rec_Buf,bufsize,0);Rec_Buf[err] = '\0';
	fputs(Rec_Buf,smtpfile);
	strcpy(line,"quit\n");
	fputs(line,smtpfile);
	bytes_sent=send(sockfd,line,strlen(line),0);
	Sleep(waittime);
	err=recv(sockfd,Rec_Buf,bufsize,0);Rec_Buf[err] = '\0';
	fputs(Rec_Buf,smtpfile);
	fclose(smtpfile);
	#ifdef WIN32
	closesocket(sockfd);
	WSACleanup();
	#else
	close(sockfd);
	#endif
}

I'm sorry if the code wasn't written very well, but I can't fix it because I don't understand it