Exchange will receive but won’t send

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Microsoft Exchange
Microsoft Windows
This morning the exchange server at my office stopped sending email. It will receive email but won't send. The queue showed 6000+ emails. After performing various troubleshooting techniques and rebooting the server it now shows 400+. On each of the emails in the queue it indicates that it could not create a connection with the destination server. I tried to do an NSLOOKUP on a couple and it came up empty. No changes that I know of have occurred. I'm thinking this may be DNS related (my weak area). Anyone have any suggestions?

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Hi!

1st STEP:
Check if your Exchange server is blacklisted on any of the ANTISPAM websites.

To do this, check up your exchange servers public IP at the following website:

If your IP address is BLACKLISTED ON ANY OF THESE SERVERS, you have to contact them for removal.

Revert back to me if this helped.

Regards,

Nilesh Roy.

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  • Ajmcgary73
    Thanks, I just looked into that but it's not listed on either of those. Any other suggestions?
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  • Stevesz
    DNS may be an issue. Have you tried pinging the servers where there are connection problems? Be aware that a ping may fail because a firewall may prohibit pinging the actual server. If you ping the servers by name, rather than IP, it will show the lookup and IP of the server. If the server is not found in DNS, the return will tell you so. You can then use a tool such as www.dnsstuff.com to verify your findings. If you are failing in your ping, but dnsstuff is succeeding, take a look at changing your DNS servers. You may find that DNS is not an issue. One of my clients does a lot of communication with various educational organizations--high schools and colleges mostly, along with some middle schools (what ever happened to junior high schools?). They do get a certain percentage of messages as undeliverable because their server is unable to communicate with the recieving server. In most cases, this is a problem at their end--the server is down, the server is misconfigured, the swerver cannot handle the mail volume, etc. There was one case, with a national hotel chain, where their public primary MX address was behing the firewall, and unreachable by anyone outside the firewall. They had a secondary MX record pointing to a server outside the firewall. A problem with Exchange failing ove rto the secondary was the culprit here. After much back and forth with their people and following a couple of MSKB articles, they changed how they had their setup, and we were able to communicate with them. I also understand that they had a good increase in the volume of mail they were recieving as well, meaning that we were not the only ones who had a problem with getting e-mail to them. Read your NDR's carefully to determine the problem(s) reported and then follow up oneach of those problems one at a time. Some you will be able to fix from your side, others will require the fix to be made by the IT personel on the other end. Steve//
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  • Nileshroy
    Hi there !! Look into your exchange server SMTP error log & copy & paste me the exact error message you are getting when the mails are NOT delivered. NOTE: I need the exact error message please, so that I can give you a solution. Regards, Nilesh Roy.
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  • Ajmcgary73
    Ok this is the error message I get in event viewer: Event Type: Warning Event Source: MSExchangeTransport Event Category: Connection Manager Event ID: 4006 Date: 10/17/2005 Time: 10:05:20 AM User: N/A Computer: KGA-MAIN Description: Message delivery to the host '66.51.205.17' failed while delivering to the remote domain 'land-5.com' for the following reason: The remote server did not respond to a connection attempt. For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp. Data: 0000: d2 02 04 c0 O..A I get this on every outgoing message on the server.
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  • Baes64
    Is there a firewall between Exchange server and the outworld?
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  • Shawnb
    Just a thought... you said over 6000 emails this morning... is that normal for your organization? If not, its possible that the exchange server was sending out spam, and your ISP has blocked outgoing email from your server. You might want to check this out if nothing else helps. -Shawn
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  • Ajmcgary73
    Yes there is a firewall, and I have verified that the smtp port is properly mapped. I fixed the 6000 email issue, the server was sending spam I have since filtered inbound connections and relays. I'm now at around 18 messages in the queue and the only ones sitting in the queue are now valid emails generated internally for transport out. I tried adding a smart host sending to the ISP's smtp server and that doesn't seem to work. Comes back saying "message delivery to host "66.51.205.17" failed while....The remote server did not respond to a connection attempt." Specs: 2003 server enterprise exchange 2003 symantec enterprise 10 symantec for exchange I've tried turning off symantec to see if that was it and no luck. I've tried adding an smtp connector to the same ISP smtp with no luck.
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  • Nileshroy
    Hi again!! See if you can send a test mail to my email address. nielsh@nileshroy.com Let me know. Regards, Nielsh Roy.
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  • Bigshybear
    There is a possibility your ISP started blocking outbound e-mails from you. Quick way to check is to go into DOS on the server and see if you can manually pull up another mail server. You said you are using Exchange so I will presume the server is running Windows. On the Exchange server, open up a DOS box and do a: telnet nileshroy.com 25 you should get back 220 karna.enmail.com ESMTP If you do, then my guess is wrong, the problem is on your mail server. If you don't, then you need to check your ISP. Your ISP may have started blocking because you were being used as a mail relay. If so they, they will open back up again after you confirm with them that you have adjusted your servers configuration. p.s. thanks Nilesh Roy BigShyBear
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  • Ajmcgary73
    Thanks for the suggestions everyone. I tried the telnet and it didn't go through. I had already sent an email to the ISP, but foolishly assumed that since it has worked trouble free for over a year why would the ISP up and filter port 25 without telling me. Well they did and after 20+ hours of teching the mail server I decided to go ahead and call them(since they never did respond to the email) and figure out what was up. Sure enough they had filtered it and had no explanation as to why in the middle of a thursday morning they would begin filtering it with no warning. Again thanks to all those who provided a response to this post it is greatly appreciated. Adam McGary
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  • Bobkberg
    And - I'd like to add kudos to you Adam. There are a fair number of threads in this forum to which a poster asks a question, several people take the time and trouble to respond, and we never hear from the poster again. Your active participation in the process has made this thread an interesting (even vibrant?) experience. Bob
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  • Nileshroy
    Good that we all could help you out :) Regards, Nilesh Roy.
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