When making a large number of connections (e.g., to a mail server) in a short amount of time, you might run out of sockets and not be able to create any more connections. The existing connections will be in a TIME_WAIT state as shown by netstat. The following articles explain this situation in more detail and include tips for how to deal with it:
Note that it seems the number of available ports has increased in Windows Server 2008.
Windows applications typically store single messages in MIME format in “.eml” files. Jakarta Mail can read these files using the MimeMessage constructor that takes an InputStream.
Windows applications typically store messages in the Windows proprietary Outlook message format in “.msg” files. Jakarta Mail can’t process these files directly, but the Apache POI project might help.