SMTP Error in C# RRS feed

  • Question

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    I sent mail using SMTP client in C# program through MS outlook 2003. Recently our mail server updated to MS outloock 2007 in server 2008.Now I can’t send mail using SMTP client in C# program. The error occur Mailbox unavailable. The server response was: 5.7.1 Unable to relay or some time Server does not support secure connections. Please help me .

    Wednesday, April 29, 2009 10:57 AM

All replies

  • Hi Prasad

    I don’t know if this will help you but I would like to inform you that this forum is dedicated to Windows Server 2008 Application compatibility and Logo certification related issues. However, the following may be helpful.

    Please check the following factors:

    ·         Check the receive connectors. Check the network property of the default connector- if you have added the IPs of the machines from where you want to run the Application.


    ·         Under Authentication Select Only TLS and externally secure option under Authentication

    ·         Select Only Exchange Server Under permission groups.


    ·         Restart the transport service and try sending emails

    You can post the Exchange server related question in the following forums:




    Hope this helps.



    Gayathri Mallya

    Wednesday, April 29, 2009 3:26 PM