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My Exchange Server 2003 will not receive email from comcast.net email users.

Posted on 2007-11-28
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Last Modified: 2008-03-27
I have a Windows 2003 Small Business Server (SP1) running Exchange server that cannot receive email from comcast.net email accounts.  I have uninstalled the Policy Patrol Spam software from the server and checked to make sure that the comcast.net domain is not blocked.  Comcast.net messages do not appear in Message Tracking.  I have checked with Comcast and they have assured me that they are not blocking the domain.  Our IP address is not on any SPAM lists and there is a correct reverse DNS entry setup with Verizon our ISP.  We are able to receive email from other domains without any problems.  Microsoft Exchange troubleshooting assistant is pointing to an outside the server problem.  I'm at a lost where else to look for the problem and I don't want to re-install the OS unless I have to.
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Question by:JFowlerjr
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by:mcse2007
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Starting point to troubleshoot..........get them to fax you a copy of NDR (non delivery report) since you are unable to receive email from them.

users from comcast.net should be able to get NDR when their emails won't go through to your mailbox.
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by:rhinoceros
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1.  Have you check Exchange log ? any e-mail message come from them ?

2. Do you have some smtp gateway, which hasl blocked this domain address ? any incoming mail record from them...

3. After you chekced, it still has no any log record, so that I also agreed "Microsoft Exchange troubleshooting assistant is pointing to an outside the server problem.."

I always has the same question from our clients. Because no incoming record in log... it means  the client server has never connected our mail server... the problem should be come from client server email blocking, BLACK list or AntiSpam rules etc.



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by:JFowlerjr
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Comcast is unwilling to send us and NDR report they have however escalated it.  I checked the log there are now messages coming from Comcast at all.  We don't have an SMTP gateway and I have confirmed with our ISP that Comcast is not blocked.  I think it is a Comcast problem but I can't prove it.

As a test if I were to connect an email server with the comcast.net domain on our private network and send email to our exchange server would this as least validate that our exchange server is not blocking the comcast email?
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by:pfma
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I'm having this exact same problem. We have an exchange 2003 server, and host our own email. I've called comcast many times. I've tried to do a telnet email message from a comcast account through smtp.comcast.net and it works fine, I get a message ID number and it says "mail accepted for delivery". I watch closely on my exchange server and spam filtering for anything coming in and there are no signs of it, while other email is just flowing right in.
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by:JFowlerjr
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I followed up with Comcast today to check the status of the ticket and they confirmed that the problem has been corrected.  They wouldn't elaborate on how the problem was solved.  When we tested it today we are still unable to receive email from comcast.net.  
We've exhausted all technical options on our side.  We have decided to have all members of our organization contact Comcast and open a support ticket on this issue to see if this will get them to cooperate.
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mcse2007 earned 250 total points
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Try this, it may or may not help you but what do you got to lost:

Get one of the IT guys in comcast.net to do a DNS lookup for your registered domain name inside their LAN  - what ever is your registered domain name for the sake of this exercise we'll call it domain.com - ok ! Give them the below instructions to ensure your SMTP internet address will show up correctly - we need this information crucially.

Further, this is your part, do this from your pc, select start>run> type in CMD
from the command prompt type nslookup then
>set type=mx
>domain.comm       <==== you should put your registered domain here

The result should show you your SMTP address plus your internet address which is your registered public ip address.

For example, when you query DELL.COM through DNS nslookup, you should get something like this.

> dell.com
Server:  nocan'tshowyoumydomain.com
Address:  192.168.1.1

Non-authoritative answer:
dell.com        MX preference = 10, mail exchanger = smtp.ins.dell.com
dell.com        MX preference = 20, mail exchanger = smtp2.ins.dell.com

smtp.ins.dell.com       internet address = 143.166.83.183
smtp2.ins.dell.com      internet address = 143.166.224.134

Now, you should expect the  IT guys from comcast.net  should tell you your internet address should match that with the internet address from your NSLOOKUP results.

What happen if they dont?

Get them to do "clear cache" their DNS server, then get them to send you an email so that their DNS server will query the internet DNS hyrachy for the correct smtp address plus its internet ip address.

Keep me posted will you ?
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by:aggressive_ed
aggressive_ed earned 250 total points
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I had this same problem, and just verified it's now working. The fix (for me anyways): I had my MX record pointing to my IP address rather than my domain name (insertdomainhere.com). I didn't realize it was a no-no. But thanks to mcse2007, I compared my own nslookup results to that of other domains, and found that they all specified domain names rather than IP's. I figured I'd do the same.

I was able to SEND email to comcast.net users, but not RECEIVE from them. But I WAS able to send AND receive to/from every other domain I had tried.

But now I can send/receive them all.

It may also be worth noting that my ISP is also comcast. Maybe thats why I was having this problem?

But I am still confused as to why the comcast users never got a "delivery failed" message.

Either way, my thanks to mcse2007. I hope this will solve JFowlerjr's problem as well.
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by:JFowlerjr
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aggressive ed:

Which MX record are you refering to; the Server side, or whoever is hosting it (Registrars side)?  Plese advise.  Thanks for this insite.....this is something we have not thought of yet.

FYI - The MX record on the our server side is using the domain name and not the IP address. however not sure what the host has.  Thanks again
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by:aggressive_ed
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Registars side.
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by:JFowlerjr
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MCSE 2007 - aggressive ed:

Aggressive ed; your post was very helpful and the points will be yours.  I was wondering if you, or you MCSE 2007 have any knowledge of what Comcast has recently done to their system.  The MX record used to work fine pointing to an IP address and since comcast has changed some of their systems, this problem arose.  Unfortunately Comcast is of little help when asked what changes need to be made from a network standpoint to comply with whatever they have done to theirs'.  This is the second issue we have had as a computer support company since comcast has made adjustments to their security, and help has come from other sources rather then comcast.  Any insite would be great!  Thanks!  
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by:aggressive_ed
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I'm also curious as to why comcast no longer is OK with an IP address for an MX record. But I have since read that everyone(except me and you, I guess) already knew this. See: http://rscott.org/dns/mx.html (step 5b)
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by:simplemojo
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I also was having this same problem.  My MX record was pointing to an IP address.  I changed the MX record to point to the A record of my email server.  This solved the problem.  Thanks for the solution.  Good Work!
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