spring mail发送邮件报错：com.sun.mail.util.MailConnectException: Couldn't connect to host

使用spring mail发送邮件的时候报以下异常：
2019-06-11 15:35:11.926 [http-nio-8090-exec-4] ERROR o.a.c.c.C.[.[localhost].[/].[dispatcherServlet] - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.mail.MailSendException: Mail server connection failed; nested exception is com.sun.mail.util.MailConnectException: Couldn’t connect to host, port: localhost, 25; timeout -1;
nested exception is:
java.net.ConnectException: Connection refused (Connection refused). Failed messages: com.sun.mail.util.MailConnectException: Couldn’t connect to host, port: localhost, 25; timeout -1;
nested exception is:
java.net.ConnectException: Connection refused (Connection refused); message exceptions (1) are:
Failed message 1: com.sun.mail.util.MailConnectException: Couldn’t connect to host, port: localhost, 25; timeout -1;
nested exception is:
java.net.ConnectException: Connection refused (Connection refused)] with root cause
java.net.ConnectException: Connection refused (Connection refused)
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at java.net.Socket.connect(Socket.java:538)
at com.sun.mail.util.SocketFetcher.createSocket(SocketFetcher.java:359)
at com.sun.mail.util.SocketFetcher.getSocket(SocketFetcher.java:238)
at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:2175)
at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:740)
at javax.mail.Service.connect(Service.java:366)
at org.springframework.mail.javamail.JavaMailSenderImpl.connectTransport(JavaMailSenderImpl.java:517)
at org.springframework.mail.javamail.JavaMailSenderImpl.doSend(JavaMailSenderImpl.java:436)
at org.springframework.mail.javamail.JavaMailSenderImpl.send(JavaMailSenderImpl.java:322)
at org.springframework.mail.javamail.JavaMailSenderImpl.send(JavaMailSenderImpl.java:311)
at com.incarcloud.ne.controller.TestAlarmController.testEmail(TestAlarmController.java:87)

检查配置发现都是正常的，最后在stackoverflow上找到答案，原来在mac或大部分linux系统上要开启postfix才能正常发送邮件

$ sudo postfix status
$ sudo postfix start

stackoverflow链接：
https://stackoverflow.com/questions/50317404/send-email-with-spring-boot-from-localhost