Error when send email message "STATUS_STACK_BUFFER_OVERRUN encountered"

I have STATUS_STACK_BUFFER_OVERRUN encountered exception.

Console:

An exception was thrown at 0x000000013FDE716D в prog.exe: 0xC0000005: access violation when reading at 0xFFFFFFFFFFFFFFFF. STATUS_STACK_BUFFER_OVERRUN encountered prog.exe caused a breakpoint. Program "[7636] Curl2.exe" ended with code -1073741510 (0xc000013a).

I get this error when sending a message by email. I want to notice that the error appears only if I send the long text. The text that I want to send takes approximately 8kb on disk in txt file. This is my code to send email:

void sendEmail(const char *server, const char *to, const char *from, const char *subject, const char *message) {
SOCKET sockfd;
WSADATA wsaData;
hostent *host;
sockaddr_in dest;
#define bufsize 300
int sent;
char line[200];
int err;
char *Rec_Buf = (char*)malloc(bufsize + 1);

if (WSAStartup(0x202, &wsaData) != SOCKET_ERROR) {
    if ((host = gethostbyname(server)) != NULL) {
        memset(&dest, 0, sizeof(dest));
        memcpy(&(dest.sin_addr), host->h_addr, host->h_length);

        dest.sin_family = host->h_addrtype;
        dest.sin_port = htons(25);

        sockfd = socket(AF_INET, SOCK_STREAM, 0);

        connect(sockfd, (struct sockaddr*)&dest, sizeof(dest));

        strcpy(line, "helo me.someplace.com\n");
        sent = send(sockfd, line, strlen(line), 0);
        Sleep(500);

        strcpy(line, "MAIL FROM:<");
        strncat(line, from, strlen(from));
        strncat(line, ">\n", 3);
        sent = send(sockfd, line, strlen(line), 0);
        Sleep(500);

        strcpy(line, "RCPT TO:<");
        strncat(line, to, strlen(to));
        strncat(line, ">\n", 3);
        sent = send(sockfd, line, strlen(line), 0);
        Sleep(500);

        strcpy(line, "DATA\n");
        sent = send(sockfd, line, strlen(line), 0);
        Sleep(500);

        strcpy(line, "To:");
        strcat(line, to);
        strcat(line, "\n");
        strcat(line, "From:");
        strcat(line, from);
        strcat(line, "\n");
        strcat(line, "Subject:");
        strcat(line, subject);
        strcat(line, "\n");
        strcat(line, message);
        strcat(line, "\r\n.\r\n");
        sent = send(sockfd, line, strlen(line), 0);
        Sleep(500);

        strcpy(line, "quit\n");
        sent = send(sockfd, line, strlen(line), 0);
        Sleep(500);

        err = recv(sockfd, Rec_Buf, bufsize, 0); Rec_Buf[err] = '\0';
        fputs(Rec_Buf, file);
        fclose(file);
#ifdef WIN32
        closesocket(sockfd);
        WSACleanup();
#else
        close(sockfd);
#endif
    }
}

I send mail through aspmx.l.google.com