I have a program on Windows that sends email via a remote SMTP server, and it is failing with an ambiguous "cannot connect" error message with no log or other information as to why it is failing. I have tested the SMTP server and confirmed it is working with the same credentials.
The program uses plaintext login to the server, as it doesn't support SSL/TLS, so the SMTP connection should be transmitted in the clear. Is there an easy way to use a packet sniffer to monitor the attempted connection, to see exactly what is being sent (in an effort to discover why the connection is failing)?