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Test DNS resolution

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  • Test DNS resolution

    I signed my company up for Microsoft Online hosted email service.

    From the get go we have had problems with items getting stuck in the outbox for minutes and warning messages in Outlook "Connection to Microsoft Exchange server has been lost".

    I'm wondering if we have a DNS issue and so am posting here.

    I have this problem with all 4 of our PCs in the office.
    They are all using Word 2007 (3 on xp, and 1 on Windows 7)

    I configured a profile for 1 of the mailboxes on my home PC and don't have a problem at home. So I think the problem is with our local network or internet connection.

    We have a T1 with 12 users (only 4 have email)

    I have reports from our T1 provider that show the total utilization is NOT excessively high during the times we are having email trouble.

    We have a windows 2003 server and all the PCs point to the server for dns. Forwarders are setup on the server pointing at our ISP DNS servers.

    DNS was not my first guess as the cause of the problem, but I'm at my wit's end.

    Is there a way to test my dns resolution from the workstations, other than an nslookup? I'm thinking of a more continuous test that may explain why the periodic drops of connection to the Exchange server.
    TIA for ANY ideas!

  • #2
    Re: Test DNS resolution

    It's not likely a DNS problem due to the caching nature of DNS. Once the relevant DNS records are resolved they'll be cached by your server for the duration of the TTL. You can find out what the TTL is by looking in the Cached Lookups folder on your DNS server (Select the Advanced option from the View menu to show the Cached Lookups folder).

    It's more likely a connectivity problem. You can check the connectivity status by holding the CTRL key and clicking on the Outlook icon in the notification tray and selecting the Connection Status item from the context menu. This might give you a clue as to whether or not you have a connectivity problem. You should see several connections to the server; one or more for the Directory and one or more for mail. Look at the response time column for each connection and look at the number of Requests/Fails. If the number of Requests/Fails are high or the response times are high then it's most likely a connectivity issue.

    Two things you can try in order to troubleshoot would be to set the option to connect via HTTP for slow and fast networks under the Exchange proxy connections (assuming you're connecting via RPC over HTTP).

    The second thing you can try is to disable cached mode (if it's enabled) to see if that improves the performance.


    • #3
      Re: Test DNS resolution

      What about OWA, does it working?

      Just to make sure that it is not a DNS issue run from your internal hosts

      nslookup yourmailserver

      Cheack that it is the same with the output of

      nslookup yourmailserver
      Csaba Papp
      MCSA+messaging, MCSE, CCNA
      Remember to give credit where credit is due and leave reputation points where appropriate