I want to protect Mail Server from SMTP Attack(many rcpt to, Unknown command,
Looping command, and Dictionary attack, etc)and DoS (Denial of Serveice) attack
as well as SPAM/JUNK/VIRUS Mail.

Is there any tool which can server these services.

Something like this can probably help you at least get started:

http://www.webumake.com/free/eximdeny.htm

You can also install different software, depending on what you are running on your machine. If you're running Cpanel, however, this is quite useful.

Thank you for your reply.
It is specifc fo Exim.

I need general Product which can serve multiple Mail servers.

Any suggestion about this .I am waiting for this.

SpamAssassin and some form of greylisting work well for me. I use Postgrey, but it's specific to Postfix I believe.

Thank you for your reply.

I am using Visnetic and Imail Mail Server.
I am looking for general tool which can protect both Mail server.

Hmm.. Should have thought of that.