Question : 550-Unrouteable address 550 Sender verify failed

I get this when i try to send email to certain address.
Was working fine untill yesterday when i had to replace my router with a different model.
zywall USG 1000. i cant pinpoint where to look.
My mail server is inhouse, dns servers are at ISP.


This is an informative message sent by mail.mydomain.com
The server was not able to deliver your email message to the following addresses:

  com> (mx1.domain.com: 550-Verification failed for
550-Unrouteable address
550 Sender verify failed)

Received: from [192.168.0.128] ([192.168.0.128])
        (authenticated user [email protected])
        by mail.mydomain.com (Kerio MailServer x.x.x)
        for [email protected]om;
        Fri, 24 Jul 2009 12:58:35 +0200
Subject:
From: My Name
Reply-To: [email protected]
To: [email protected]om
Content-Type: text/plain
Date: Fri, 24 Jul 2009 13:08:09 +0200
Message-Id: <1248433689.21179.39.camel@name-32171de48.mylandomain.local>
Mime-Version: 1.0
X-Mailer: Evolution 2.12.0
Content-Transfer-Encoding: 7bit

Answer : 550-Unrouteable address 550 Sender verify failed

it works now.
all of it.

what i did that could have caused the problem:

i added another zone to my internal dns that says that www.mydomain.com is located on address 192.168.0.x
also did the same for mx and A for mx.

then i could access my web from lan. But this email problem started appearing. i deleted the zone but the problem remained so i concluded it was not dns zone problem. probably all it took was the time to update the zone deletion?

now i have a problem is i dont know how to tell my internal dns to access internal address for www.mydomain.com, and the same for my email server.