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NDR 554 5.7.1 - Emails cant be sent - Exchange 2010

Hi All

I'm just looking for validation here more than anything else.

I have recently moved offices and as part of that we started using a new ISP, who gave us a new range of Public IP's.  External DNS has been updated and my Hub Transport server is receiving emails fine internally and externally.

When however we send them externally I get the above NDR.  We use Maildefender as a smart host and so I'm wondering if its just a case that they are blocking the emails based on the fact that they don't have details of our new Public IP address?

Or is there anything else that I need to check before going to them?

I will post the NDR in the next message for people to cast judgement.



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8/22/2022 - Mon
Gareth Gudger

Sounds like you need to update them with your new Public IPs. Do you have an admin portal you can check this on?

I think its going to be more of a phone call as they only allow us to put in the recipient details

Do you think Im on the right track though?
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Gareth Gudger

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nashim khan


You can check the below steps:-
 I experienced the same error for the last couple of days. I realized that I changed the relay configuration to "authenticated users" only and the server wasn't working as I expected.
To solve the problem I did the following steps:
Open the Exchange System Manager;
Go in Administrative Groups -> Administrative group name -> Server -> Server name -> Protocols -> SMTP;
Right click on Default SMTP Virtual Server -> properties;
Access tab -> Relay buttom;
Select "only the list bellow" and add your domain and\or IPs you do want to allow the relay
 and finally check  the "Allow all computers witch successfully authenticate to relay, regardless of the list above" checkbox.

Link is here.

or check this below one also.
Simon Butler (Sembee)

@ nashimkhan123 - you have posted Exchange 2003 instructions. Try reading the question rather than posting the first thing a Google answer throws up.

Without the full NDR it is impossible to know the exact problem.
However as you using a new IP address range it is probably a missing DNS or PTR record. Check with the new ISP if a PTR is set, if it is, it should match the DNS record pointing at Exchange and be the same as the FQDN on the Send Connector.

Ensure the NAT is correct on your firewall so the Exchange traffic is going out with the correct external IP address.

Gareth Gudger

I guess I was making the assumption you were using MailDefender for outbound filtering when you said you were using it as a smarthost. Is this correct?
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nashim khan


Have you checked the other link which i have posted on it. If not then please check. Because no one is perfect, hence forth i am trying the same to become perfect dude.
Simon Butler (Sembee)

@ nashimkhan123 - Read the EE guidelines about blind links.

No one is perfect, but posting an answer about a completely different version of Exchange is a waste of everyone's time.


first i will ask you to check  are you able to ping your new IP from outside or check MX record and all . If suppose your IP is not pinging from below network tool then it mean you have internal issue on your network where your public IP is not reaching till your gateway


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William Peck

Accepted as they were quickest to reply and also pointed me in the right direction.