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MS Exchange 2003 changing Internet providers

Hello, I have recently changed Domain services and then shortly after T-1 providers. It appears after changing T-1 providers when sending emails to some destinations a delayed response is returned and the emails time out and get rejected. These are valid emails and even when replying to some of these emails it will time out. Is there something I am missing in Exchange now that the T-1 has changed. This is a single exchange server with no front end. Set with a Private IP mapped to a new public IP address.
2 Solutions
what are the error codes:
Can you send mail to these servers manually from your exchange server?

get the mx record for a recipient domain, and telnet to it on port 25 following the below instructions

Have you checked your rDNS or if your new IP is on any sort of blacklist? (manual email test linked above should prove this, and give you an error code)
There are three usual problems when ISPs are changed.

1. Reverse DNS is not set, or set incorrectly. You need to speak the ISP to get that changed.
2. A smart host is configured either on an SMTP Connector or on the SMTP virtual server pointing at a server at the old ISP.
3. DNS servers are set incorrectly. There should be no external DNS servers in any of the network configuration of any machine on the network, nor on the SMTP virtual server. Check on your domain controllers in the DNS Server applet to ensure that any forwarders have been updated.

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