System.Net.Mail SMTP How Do I Write Code Using WinSock Under .NET ?

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System.Net.Mail SMTPHow Do I Write Code Using WinSock Under .NET ?Problem: Failure of in-house written VB.Net that uses System.Net.Mail to send an SMTP message through a relay server.Systems: About 100 Windows XP, Professional, Version 2002, SP2 clients. VB.Net 2005Symantec 10.1.6.6010. All Microsoft patches are regularly installed.Symptoms: About 5% of the SMTP messages are not being sent. All client workstations are affected.Research 1: Added code to trap error and got error number -2147220973 and error description, “The transport failed to connect to the server”.Research 2: Verified that the failed messages were 'not' leaving the client by using a hardware network sniffer.Research 3: Used SysInternals / Network Monitor 3.3, to monitor the process and confirmed that some messages were not sent. That is, 'no' communication was initiated by the workstation with the relay server.My guess is that when Winsock attempts to establish a socket it fails.Request: How can I diagnose this problem?Thanks,Bunk-question by Bunk