Some websites checking HTTPS, SMTP over TLS, and SMTP.

Check HTTPS:
https://www.ssllabs.com/

Check SMTP over TLS:
https://www.checktls.com/

Check SMTP:
https://www.wormly.com/test-smtp-server

A Perl script to verify if your SMTP server has enabled SMTP over TLS.

#!/usr/bin/perl
use IO::Socket;
$|=1;

if(($#ARGV + 1 ) != 2){
        die "Usage: $0 host_ip smtp_port\n";
}

$host_ip=shift;
$smtp_port=shift;

$sock=IO::Socket::INET->new(PeerAddr => "$host_ip:$smtp_port", Timeout => 5) || die "$host_ip:$smtp_port is closed!\n";
$sock->recv($mem, 1000, 0);
$sock->send("EHLO test.com\r\n");
$sock->recv($mem2, 5000, 0);
$sock->shutdown(2);

if(lc($mem2)=~m/starttls/){
        print "$host_ip:$smtp_port supports SMTP over TLS!\n";
}else{
        print "$host_ip:$smtp_port does not support SMTP over TLS!\n";
}

exit(1);