Comcast emails delayed then not delivered

Hi,

We recently changed our external IP's and mx records to a new address. Since then we have not been able to get to anyone @comcast.net. I have contacted our provider and made sure we have the reverse DNS happening as well as our PTR updated. All is well for other recipients. HEre is the error I get back. Any ideas?

Thanks!!

Your message did not reach some or all of the intended recipients.

      Subject:      Testing email account
      Sent:      6/26/2009 9:09 AM

The following recipient(s) cannot be reached:

      customer@comcast.net on 6/28/2009 9:14 AM
            Could not deliver the message in the time limit specified.  Please retry or contact your administrator.
            <mail.mycompany.com #4.4.7>
Darktide00Asked:
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Alan HardistyCo-OwnerCommented:
How long ago did you change your DNS records?
It usually takes about 48 hours for the DNS changes to propogate around the world, so they may have some catching up to do.
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Alan HardistyCo-OwnerCommented:
Does your email get delivered directly to your server or do you receive mail via a 3rd party?
If via a 3rd party, they may have issues.
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Alan HardistyCo-OwnerCommented:
Check your new IP on blacklists http://www.mxtoolbox.com/blacklists.aspx
Check to see if you have an SMTP connector set to send out email via a Smart Host as if you have changed IP's you will need to change Smart hosts if you used your old ISP's mail servers.
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Darktide00Author Commented:
Hi,

We changed it two weeks ago. We have an Exchange 2003 server in house. I went to the link and we are not blacklisted in any way.
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Alan HardistyCo-OwnerCommented:
Okay - check your SMTP Connector(s) to see if you are using a Smart Host:
  1. Start Exchange System Manager.
  2. Expand the Connectors container.
  3. Right-click the default SMTP Connector and choose properties.
  4. On the General Tab - check to see if using a Smart Host or using DNS to route mail.
  5. Check any other Connectors.
  6. If any use a Smart Host, is the Smart Host your old ISP's Smart Host?  If it is, change it to your new ISP's Smart Host.
     
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Darktide00Author Commented:
We are using DNS for this connector, I am not showing any other connectors here.
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Alan HardistyCo-OwnerCommented:
Comcast may not like your new IP.
Please try setting up a new SMTP Connector to send comcast mails via your new ISP's smart host:
http://www.msexchange.org/tutorials/Configuring-SMTP-Connector.html
Just add @comcast.net to the address space and ask your new ISP if you need to authenticate the connection.
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Darktide00Author Commented:
I am not sure if we were blocked and my request to unblock went through or if the connector fixed it but either way I learned a lot and everything is ok now.

Thanks!!!
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