javax.mail.MessagingException：无法连接到SMTP主机：192.168.90.157，端口：25

Question

发送电子邮件时遇到问题。

javax.mail.MessagingException: Could not connect to SMTP host: 192.168.90.157, port: 25;
      nested exception is:
        java.net.ConnectException: Connection refused: connect
        at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1706)
        at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:525)
        at javax.mail.Service.connect(Service.java:291)
        at javax.mail.Service.connect(Service.java:172)
        at javax.mail.Service.connect(Service.java:121)
        at javax.mail.Transport.send0(Transport.java:190)
        at javax.mail.Transport.send(Transport.java:120)
        at SendEmail.main(SendEmail.java:29)
    Caused by: java.net.ConnectException: Connection refused: connect
        at java.net.PlainSocketImpl.socketConnect(Native Method)
        at java.net.PlainSocketImpl.doConnect(Unknown Source)
        at java.net.PlainSocketImpl.connectToAddress(Unknown Source)
        at java.net.PlainSocketImpl.connect(Unknown Source)
        at java.net.SocksSocketImpl.connect(Unknown Source)
        at java.net.Socket.connect(Unknown Source)
        at java.net.Socket.connect(Unknown Source)
        at com.sun.mail.util.SocketFetcher.createSocket(SocketFetcher.java:284)
        at com.sun.mail.util.SocketFetcher.getSocket(SocketFetcher.java:227)
        at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1672)
        ... 7 more