Only some user's can not send to a specific domain with Exchange 2003 Sp1

I have a client that is running Exchange 2003 Sp1 and has 3 main users.  2 of the users can not send emails to the domain kstooldie.com, but one of them can.  They are all connected to the domain and exchange server exactly the same way, and all other emails work fine.  The 2 users that cannot send to the domain get this error message back...

There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<allisonsentry.com #5.5.0 smtp;550 <callison@kstooldie.com>: Recipient address rejected: No such domain at this location (callison@kstooldie.com)>

...any ideas?
wisconsinpcAsked:
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marce_litoCommented:
it may be a problem with the destination domain blocking some of your client's addresses
SembeeCommented:
That domain is using Road Runner servers, so that could be a problem. Road Runner are particularly picky about spam being delivered to their servers.

http://www.dnsreport.com/tools/dnsreport.ch?domain=kstooldie.com

Running the same report on your domain flags up an error.
http://www.dnsreport.com/tools/dnsreport.ch?domain=allisonsentry.com

It is the classic what the server announces itself as.
Change that to mail.allisonsentry.com in ESM, Servers, <your server>, Protocols, SMTP. Right click on the SMTP VS and choose Properties. Click on the tab Delivery and the Advanced. Change the FQDN to mail.allisonsentry.com - don't bother with Check DNS as that will probably fail.

If that doesn't fix it, use message tracking to see if the messages are being delivered to the same server.

Simon.

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