SMTP Failure : to send Email for a specific scenario RRS feed

  • Question

  • We have a VB.NET 4.0 application installed in "Windows 2012 R2 Std 64-bit" server,
    which was working perfectly since the last 7-8 months with the Lotus Notes SMTP server.
    The apps were able to send email's perfectly.

    Now, the team has changed the SMTP server,
    And for a particular application which was working fine before, we are seeing the "Failure sending mail" error.
    Now this scenario is not seen for application's which are sending 1 time email to multiple users.
    This scenario is seen only in the application which sends multiple emails to multiple users one after another in a loop.

    We have also seen an intermittent error  while trying to send email via PowerShell from the same server.
    The error says "Unable to read data from the transport connection: net_io_connectionclosed"
     We believe this can be the reason for the error in the application too, but we are not sure.

    Also, when we de-bug the application using breakpoints, we normally don't see the "failure sending email" error but this is also an intermittent case . But without breakpoints, it shows the error.

    Please help us in priority.

    • Edited by MohanReddyM Wednesday, June 6, 2018 10:07 AM
    Wednesday, June 6, 2018 10:01 AM

All replies

  • Hi,

    Have a nice day! Thanks for your question.

    This issue signs that "Unable to read data from the transport connection: net_io_connectionclosed" when sending email. Based on this specific situation, we could use Netmon tool to trace the network and capture interactive packets between client and Mail server.

    Microsoft Network Monitor 3.4 (archive)

    Further, here is a link about this issue for your reference. At the same time, we’d consult your Lotus Notes vendor for the resolution.

    Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

    Hope this helps. If you have any question and concern, please feel free to let me know.

    Best regards,


    Please remember to mark the replies as an answers if they help.
    If you have feedback for TechNet Subscriber Support, contact

    Thursday, June 7, 2018 5:28 AM
  • Thank you Michael
    Friday, June 8, 2018 12:06 PM