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MPI is not part of Connect. There are several MPIs available like OpenMPI: https://www.open-mpi.org/ , MirthMatch etc., you need to create an Adapter to connect to these MPIs. An example to connect to MPI is also available in our WiKi page: 'Create an MPI Adapter'
How do I configure what certificate should be used to properly authenticate the request?
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CONNECT uses the Direct JAVA RI for retrieving certs via DNS. The logic used there is that it checks for an individual cert first, in your case it would be admin.mail.testserver.com, and if this CERT record isn’t found then it will look for the organization cert at mail.testserver.com.
The PKIX path errors are because one machine doesn't trust the other.
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Adding the system property '-Djavax.net.debug=ssl' to your jvm. This will output some pretty verbose logging but have found that it's a good way to track the the SSL handshake.
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