Q: javax.mail.MessagingException: Could not connect to SMTP host: xxx.domain.com, port: 25;
   nested exception is:
	java.net.SocketException: Software caused connection abort: connect
	at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1213)
	at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:311)
	at javax.mail.Service.connect(Service.java:255)
	at javax.mail.Service.connect(Service.java:134)
	at javax.mail.Service.connect(Service.java:86)
	at com.sun.mail.smtp.SMTPTransport.connect(SMTPTransport.java:144)

A: Based on the error message "Software caused connection abort: connect", it could be
   caused by some anti-virus software blocking the port 25. Check your port blocking rule.

   The command line telnet is also very help:
   telent mail.server-or-ip-address 25
   EHLO mail.server-or-ip-address
   QUIT

   If the error is "Connection refused", then the server is probably not running,
   use netstat -aon to find the service is running.

   If the error is "Connection failed", then the firewall and/or anti-virus software may be blocking the port.