TIBCO Spotfire Automation Services error:"Failure sending mail. Unable to read data from the transport connection: net_io_connectionclosed".

Product:TIBCO Spotfire Automation Services
Versions:7.0 and prior

Summary:
Error when using TIBCO Spotfire Automation Services: "Failure sending mail. Unable to read data from the transport connection: net_io_connectionclosed". This can happen if there are issues connecting to the SMTP server.

Details:
Description:
Automation Services throws an error when sending e-mail.
Symptoms:
Spotfire.Dxp.Automation.log error entry:
---------------------------------------------------------------------------------
The task 'Send Email' could not be executed.
System.Net.Mail.SmtpException: Failure sending mail. ---> System.IO.IOException: Unable to read data from the transport connection: net_io_connectionclosed.
   at System.Net.Mail.SmtpReplyReaderFactory.ProcessRead(Byte[] buffer, Int32 offset, Int32 read, Boolean readLine)
   at System.Net.Mail.SmtpReplyReaderFactory.ReadLines(SmtpReplyReader caller, Boolean oneLine)
   at System.Net.Mail.SmtpReplyReaderFactory.ReadLine(SmtpReplyReader caller)
   at System.Net.Mail.SmtpConnection.GetConnection(ServicePoint servicePoint)
   at System.Net.Mail.SmtpClient.Send(MailMessage message)
   --- End of inner exception stack trace ---
   at System.Net.Mail.SmtpClient.Send(MailMessage message)
   at Spotfire.Dxp.Automation.Tasks.SendEmail.SendTheMail(TaskExecutionContext context, String smtpHost, String fromAddress, String messageBody, AttachmentsInfo attachmentsInfo)
Done
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Cause:
This error message indicates an issue connecting to the SMTP server.

Resolution:
This issue is related to connection to SMTP server so check if the application request (Automation Services) is being blocked on the SMTP server. Couple of checks you can perform are:

> Check if there is any communication problem between Automation Services server and SMTP server using "telnet"command from both machines.