Exchange 2010 Receives But Does Not Send Email To Internet

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I had same issue and ISP said they are not blocking, The I requested to speak to a higher level tech and they said they need to open port 25 from their end..So check with them to see if they have port 25 going out blocked or if they are using a different port to route mail externally, if so then you may need to change this on your external send connector. I will be suprise if this have anything to do with Cisco

Ok, let us know what you find out from your firewall guys tomorrow. Bottom line is that we have fixed some misconfigurations with the multiple send connectors so don't put those back. Keep one outbound send connector. I would suggest not enabling external DNS lookup on the send connector. If you do, make sure that you specify external DNS servers to use. Let us know what happens.
Do you have a one-to-one NAT configured for your Exchange server that corresponds to the IP listed on your MX records? If so, check to make sure that your domain is not listed on any Real-time Black Lists (RBL's). You can check here:

Ok, check the basics. You may need to get your " Cisco" guys involved. Start with your DNS MX record. Have you created a MX record that points to the IP address assigned to you by your Internet Service Provider (ISP)? You will then need to allow inbound traffic over SMTP (port 25) to access that public IP. You will also need to make sure that you have a Network Address Translation (NAT/PAT) rule configured to forward traffic destined for your public IP and SMTP (port 25) to your Exchange server responsible for accepting messages (Edge Transport or Hub Transport). If this is setup correctly, you should be able to telnet to other email (SMTP) servers FROM your Exchange server. If you can't, then your firewall configuration needs to be corrected. Also check any Windows Server firewall settings to ensure that they are not blocking this traffic.
I got to talk to both the ISP and the Network guy and they said smtp 25 is wide open. My Windows Firewall is turned off. I cannot access smtp 25 on external websites/mail servers from any of my clients here or Exchange Server.

I will not know if there is any other way/tool I can use to trace where the smtp connection is failing.

I tried using network monitor to fix this and I noticed that all the Telnet and SMTP based protocol is going thru my LAN interface. The External Interface that is facing the internet is not seeing the traffic.

Please how do I direct all the traffic from the local adapter on the Exchange Server to the External Adapter

I found out I had a Default Gateway on my Local Network Interface. I had to remove it and everything worked like a magic.

Thanks to you all and network monitor, it is a great tool.

Thanks TWHarrignton.
I had the same issue as you.

The problem is the gateway can't be removed since it is connect to the internet thru router.

if removed, no internet connection will appear.

Can anyone give any suggestion, please.


I found out I had a Default Gateway on my Local Network Interface. I had to remove it and everything worked like a magic.

Thanks to you all and network monitor, it is a great tool.

Thanks TWHarrignton.
To be clear: they are talking about removing the gateway on the second NIC in the Exchange server box. In my network we use the gateway on the Internet-facing network card and leave the gateway field facing the local network card blank.
thanks for your info.

My network config looks fine, however i had the same symptom and can't send email out to other domain.

btw, i can telnet, and receive mail.

what i notice is source ip :, anything go wrong?
Status: Ready

Size (KB): 1

Message Source Name: FromLocal

Source IP:

SCL: -1

Date Received: 12/9/2012 9:15:24 PM

Expiration Time: 12/11/2012 9:15:24 PM
That is the network mask. It should have your IP address or the local network IP address.

sorry, my typo

Below is from message quene:

Status: Ready

Size (KB): 2

Message Source Name: FromLocal

Source IP:

SCL: -1

Date Received: 12/9/2012 9:07:46 PM

Expiration Time: 12/11/2012 9:07:46 PM

Last Error:

What I notice is source : , boardcast ip address, is this the problem arise

As it is a boradcast, it will treat as spam when connecting to other mail server?
Something in not configured correctly. is not a valid IP address. That error message should either have your local ip (eg or your internet IP (eg
yep, that's the problem

1)anything can do in setting the send connector use the private ip add?

2) If using IPV6, there is no problem.

However, Exchange how to setup use IPV6 for send mail

I already added entry for ipv6 in exchange and enabling the ipv6

btw, I had the problem both in exchange and hmail
What version of Exchange is this? Do you have two network cards in the exchange box?

You can set up a smarthost to route via a specific SMTP (such as at your isp).
i m using Exchange 2010

Now using one network card connect to router. other service is ok except smtp.

But i can telnet 25 from outsider. The sympton is very similar to the case. if i go without router or (hmail)IPV6 enabled, it's no problem.

i tried use smart host, howver still had the "cannot connect to" problem ( address)
That is an invalid address - you need to figure out where its picking it up from.
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