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  • Connection Dropped by remote host

    We seem to be having some issues with sending email from our Exchange 2003 server to outside addresses with attachments. If we send a small piece of mail, then it appears that the emails go through, but it seems that if we try to email attachments bigger then around 2MB they don't go through.

    I've checked the SMTP logs and I'm not seeing obvious errors, just the emails are stuck in the outgoing queues.

    Things I've checked:
    Global Settings-Message Delivery-Defaults-Sending message size is set to 30MB.
    Server-Protocols-SMTP-SMTP Server-Messages-Limit message size is not set

    Example of SMTP log:

    220 mx.google.com ESMTP gk6si8481066pbc.35
    ourserver.domain.com
    250-mx.google.com at your service [123.456.789]
    FROM:<[email protected]> SIZE=10983951
    250 2.1.0 OK gk6si8481066pbc.35
    TO:<[email protected]>
    250 2.1.5 OK gk6si8481066pbc.35
    -
    354 Go ahead gk6si8481066pbc.35

    Any place I can look to try to see what's going on?

    Thanks!!!

  • #2
    Re: Connection Dropped by remote host

    I believe there is a third place for message limits - SMTP virtual connector.
    Have you checked this?

    Edit: On second thoughts, if it were a limit implication, i would expect a message bounced to the sender before attempting to send.

    Is that the message from the queue, or the SMTP log? I thought SMTP logging is more detailed than that.

    Assuming your configuration is correct and there are no transport issues, you could send a test to a Gmail account which accepts up to 25MB.

    Hope this helps.
    Last edited by simonsays; 10th August 2012, 14:39.

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    • #3
      Re: Connection Dropped by remote host

      Simon,

      Thanks for the reply.

      Routing Groups-Group-Default Connector-Content Restrictions-Allowed Sizes-Not set.

      Edit: Sorry...didn't see your edit...the Connection Dropped By Remote Host is from Admin Groups-Server-Queues. I see all the queues listed and the messages stuck in each queue. When I select a queue, the Connection Dropped message appears under the Additional queue information section.

      I've tried several different recipients, GMail among them, and same result. For a test, I sent email to my personal account, RCN, with an attachment. That message will not go through. If I delete it from the queue and send another message without an attachment, it works just fine.
      Last edited by jp1; 10th August 2012, 14:49.

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      • #4
        Re: Connection Dropped by remote host

        Primary cause of this is outside of Exchange.
        Third party interference, could be AV, Antispam, file level AV scanning something it shouldn't do, a firewall (Cisco in particular) scanning SMTP traffic etc.

        Simon.
        --
        Simon Butler
        Exchange MVP

        Blog: http://blog.sembee.co.uk/
        More Exchange Content: http://exchange.sembee.info/
        Exchange Resources List: http://exbpa.com/
        In the UK? Hire me: http://www.sembee.co.uk/

        Sembee is a registered trademark, used here with permission.

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        • #5
          Re: Connection Dropped by remote host

          Thanks Sembee.

          I disabled AV on the Exchange server, no luck. I'm going to get my ISP involved. They manage our Cisco ASA, so I'll have them check the logs on it to see if that offers any clue.

          Comment


          • #6
            Re: Connection Dropped by remote host

            You normally need to disable and uninstall the AV, plus reboot the server, for it to be fully removed
            Tom Jones
            MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
            PhD, MSc, FIAP, MIITT
            IT Trainer / Consultant
            Ossian Ltd
            Scotland

            ** Remember to give credit where credit is due and leave reputation points where appropriate **

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            • #7
              Re: Connection Dropped by remote host

              If you have a Cisco ASA device then that is probably the cause. It has a feature called Mail Guard (I think that is the new name), also known as fixup SMTP which is notorious for causing problems with email delivery. It needs to be disabled on the Cisco device.

              Simon.
              --
              Simon Butler
              Exchange MVP

              Blog: http://blog.sembee.co.uk/
              More Exchange Content: http://exchange.sembee.info/
              Exchange Resources List: http://exbpa.com/
              In the UK? Hire me: http://www.sembee.co.uk/

              Sembee is a registered trademark, used here with permission.

              Comment


              • #8
                Re: Connection Dropped by remote host

                Ossian...I'll remove AV completely today and give her a reboot once the business day is done.

                If that doesn't help, I'll contact ISP about the fixup SMTP.

                It appears that some large emails did eventually get delivered hours later. For example, I sent a message at 1339 on Friday and the recipient eventually received it at 0012 Saturday morning. Very strange.

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                • #9
                  Re: Connection Dropped by remote host

                  Originally posted by Ossian View Post
                  You normally need to disable and uninstall the AV, plus reboot the server, for it to be fully removed
                  Yep, i had a call logged with MS for delivery issues back last year and disabling wasn't enough for them.

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                  • #10
                    Re: Connection Dropped by remote host

                    Get the fixupSMTP feature disabled whether or not the problem is resolved. It will cause you problems eventually.

                    Simon.
                    --
                    Simon Butler
                    Exchange MVP

                    Blog: http://blog.sembee.co.uk/
                    More Exchange Content: http://exchange.sembee.info/
                    Exchange Resources List: http://exbpa.com/
                    In the UK? Hire me: http://www.sembee.co.uk/

                    Sembee is a registered trademark, used here with permission.

                    Comment


                    • #11
                      Re: Connection Dropped by remote host

                      Just checked and fixupSMTP was disabled, as was inspect smtp.

                      However, I think I found the solution to my woes.

                      Seems we were also having issues downloading large files (no one bothered to tell me). The DL session would disconnect in the middle. ISP had me plug a laptop directly into the back of the ASA and I was able to download large files with no issues at all. This lead me to something wrong on the internal network. So, as a simple test I plugged the ASA back into our network, but on a different port. Lo and behold, DL's worked fine and large emails are now being sent again. We don't have any VLAN's setup or MAC restricting. I'll take a look at the settings of the port that the ASA was on to see if there was something set that might of caused this.

                      Simply moving the ASA to a different port worked. Never would of thought to try that at all. Sometimes in my search to fix something I overlook simple things.

                      Thanks for all the suggestions and advice. It did lead me in the right direction...much appreciated!

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                      • #12
                        Re: Connection Dropped by remote host

                        Glad you got it sorted!

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