100's Of Spam Emails Per Hour

I'm getting literally about 100 of these per hour easy in whm > mail queue! Where is it coming from and how do I stop this?

1JBOml-0008CW-Fz-H
mailnull 47 12
<>
1199600103 0
-ident mailnull
-received_protocol local
-body_linecount 33
-max_received_linelength 115
-allow_unqualified_recipient
-allow_unqualified_sender
-localerror
XX
1
root@server.domain.com

154P Received: from mailnull by server.domain.com with local (Exim 4.68)
id 1JBOml-0008CW-Fz
for root@server.domain.com; Sun, 06 Jan 2008 00:15:03 -0600
038 X-Failed-Recipients: admin@domain.com
029 Auto-Submitted: auto-replied
063F From: Mail Delivery System <Mailer-Daemon@server.domain.com>
029T To: root@server.domain.com
059 Subject: Mail delivery failed: returning message to sender
052I Message-Id: <E1JBOml-0008CW-Fz@server.domain.com>
038 Date: Sun, 06 Jan 2008 00:15:03 -0600

1JBOml-0008CW-Fz-D
This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

admin@domain.com
SMTP error from remote mail server after RCPT TO:<admin@domain.com>:
host sentry.domainbank.com [64.85.73.28]: 553 sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1)

------ This is a copy of the message, including all the headers. ------

Return-path: <root@server.domain.com>
Received: from root by server.domain.com with local (Exim 4.68)
(envelope-from <root@server.domain.com>)
id 1JBOmk-0008CJ-To
for admin@domain.com; Sun, 06 Jan 2008 00:15:02 -0600
To: admin@domain.com
Subject: Services(2) failed
From: monitor@domain.com
Message-Id: <E1JBOmk-0008CJ-To@server.domain.com>
Date: Sun, 06 Jan 2008 00:15:02 -0600

Address:domain.com

Following services are down:

SSH(22)
MySQL(3306)