我已将spring-boot-starter-email 2.1.1.RELEASE添加到我的spring boot应用程序中，并配置了JavaMailSender。在Spring Boot应用程序启动时，运行状况检查会启动，并在日志记录中警告SSLSocket双工关闭失败。但是，应用程序启动了，我能够从我的应用程序发送电子邮件。但是每次我发送电子邮件时，我的日志记录中都会显示相同的警告。
我正在使用JDK 11 + 28
我正在针对本地邮件服务器运行，我的春季启动配置是：
spring.mail.protocol=smtp
spring.mail.host=localhost
spring.mail.port=20465
spring.mail.username=test
spring.mail.password=test
spring.mail.properties.mail.debug=true
spring.mail.properties.mail.smtp.starttls.enable=true
spring.mail.properties.mail.smtp.starttls.required=true
spring.mail.properties.mail.smtp.auth=true
spring.mail.properties.mail.smtp.port=20465
spring.mail.properties.mail.smtp.connectiontimeout=5000
spring.mail.properties.mail.smtp.timeout=5000
spring.mail.properties.mail.smtp.writetimeout=5000
我在日志中得到以下结果：
DEBUG: JavaMail version 1.6.2
DEBUG: successfully loaded resource: /META-INF/javamail.default.address.map
DEBUG: getProvider() returning javax.mail.Provider[TRANSPORT,smtp,com.sun.mail.smtp.SMTPTransport,Oracle]
DEBUG SMTP: useEhlo true, useAuth true
DEBUG SMTP: trying to connect to host "localhost", port 20465, isSSL false
220 partners4it.nl ESMTP Postfix (Ubuntu)
DEBUG SMTP: connected to host "localhost", port: 20465
EHLO kopsjero-XPS-15-9560
250-mydomain.nl
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN CRAM-MD5 DIGEST-MD5 NTLM
250-AUTH=PLAIN LOGIN CRAM-MD5 DIGEST-MD5 NTLM
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
DEBUG SMTP: Found extension "PIPELINING", arg ""
DEBUG SMTP: Found extension "SIZE", arg "10240000"
DEBUG SMTP: Found extension "VRFY", arg ""
DEBUG SMTP: Found extension "ETRN", arg ""
DEBUG SMTP: Found extension "STARTTLS", arg ""
DEBUG SMTP: Found extension "AUTH", arg "PLAIN LOGIN CRAM-MD5 DIGEST-MD5 NTLM"
DEBUG SMTP: Found extension "AUTH=PLAIN", arg "LOGIN CRAM-MD5 DIGEST-MD5 NTLM"
DEBUG SMTP: Found extension "ENHANCEDSTATUSCODES", arg ""
DEBUG SMTP: Found extension "8BITMIME", arg ""
DEBUG SMTP: Found extension "DSN", arg ""
STARTTLS
220 2.0.0 Ready to start TLS
javax.net.ssl|DEBUG|19|RMI TCP Connection(2)-127.0.0.1|2019-02-14 13:04:23.007 UTC|SSLCipher.java:437|jdk.tls.keyLimits: entry = AES/GCM/NoPadding KeyUpdate 2^37. AES/GCM/NOPADDING:KEYUPDATE = 137438953472
EHLO kopsjero-XPS-15-9560
250-mydomain.nl
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-AUTH PLAIN LOGIN CRAM-MD5 DIGEST-MD5 NTLM
250-AUTH=PLAIN LOGIN CRAM-MD5 DIGEST-MD5 NTLM
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
DEBUG SMTP: Found extension "PIPELINING", arg ""
DEBUG SMTP: Found extension "SIZE", arg "10240000"
DEBUG SMTP: Found extension "VRFY", arg ""
DEBUG SMTP: Found extension "ETRN", arg ""
DEBUG SMTP: Found extension "AUTH", arg "PLAIN LOGIN CRAM-MD5 DIGEST-MD5 NTLM"
DEBUG SMTP: Found extension "AUTH=PLAIN", arg "LOGIN CRAM-MD5 DIGEST-MD5 NTLM"
DEBUG SMTP: Found extension "ENHANCEDSTATUSCODES", arg ""
DEBUG SMTP: Found extension "8BITMIME", arg ""
DEBUG SMTP: Found extension "DSN", arg ""
DEBUG SMTP: protocolConnect login, host=localhost, user=test, password=<non-null>
DEBUG SMTP: Attempt to authenticate using mechanisms: LOGIN PLAIN DIGEST-MD5 NTLM XOAUTH2
DEBUG SMTP: Using mechanism LOGIN
DEBUG SMTP: AUTH LOGIN command trace suppressed
DEBUG SMTP: AUTH LOGIN succeeded
QUIT
221 2.0.0 Bye
javax.net.ssl|DEBUG|19|RMI TCP Connection(2)-127.0.0.1|2019-02-14 13:04:23.185 UTC|SSLSocketImpl.java:473|duplex close of SSLSocket
javax.net.ssl|DEBUG|19|RMI TCP Connection(2)-127.0.0.1|2019-02-14 13:04:23.186 UTC|SSLSocketImpl.java:1361|close the underlying socket
javax.net.ssl|DEBUG|19|RMI TCP Connection(2)-127.0.0.1|2019-02-14 13:04:23.186 UTC|SSLSocketImpl.java:1380|close the SSL connection (initiative)
javax.net.ssl|DEBUG|19|RMI TCP Connection(2)-127.0.0.1|2019-02-14 13:04:23.187 UTC|SSLSocketImpl.java:636|close inbound of SSLSocket
javax.net.ssl|WARNING|19|RMI TCP Connection(2)-127.0.0.1|2019-02-14 13:04:23.189 UTC|SSLSocketImpl.java:494|SSLSocket duplex close failed (
"throwable" : {
java.net.SocketException: Socket is closed
at java.base/java.net.Socket.shutdownInput(Socket.java:1521)
at com.sun.mail.util.WriteTimeoutSocket.shutdownInput(WriteTimeoutSocket.java:281)
at java.base/sun.security.ssl.BaseSSLSocketImpl.shutdownInput(BaseSSLSocketImpl.java:218)
at java.base/sun.security.ssl.SSLSocketImpl.shutdownInput(SSLSocketImpl.java:651)
at java.base/sun.security.ssl.SSLSocketImpl.bruteForceCloseInput(SSLSocketImpl.java:606)
at java.base/sun.security.ssl.SSLSocketImpl.duplexCloseOutput(SSLSocketImpl.java:566)
at java.base/sun.security.ssl.SSLSocketImpl.close(SSLSocketImpl.java:479)
at com.sun.mail.smtp.SMTPTransport.closeConnection(SMTPTransport.java:1425)
at com.sun.mail.smtp.SMTPTransport.close(SMTPTransport.java:1418)
at org.springframework.mail.javamail.JavaMailSenderImpl.testConnection(JavaMailSenderImpl.java:400)
at org.springframework.boot.actuate.mail.MailHealthIndicator.doHealthCheck(MailHealthIndicator.java:43)
at org.springframework.boot.actuate.health.AbstractHealthIndicator.health(AbstractHealthIndicator.java:84)
at org.springframework.boot.actuate.health.CompositeHealthIndicator.health(CompositeHealthIndicator.java:98)
at org.springframework.boot.actuate.health.HealthEndpoint.health(HealthEndpoint.java:50)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.springframework.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:246)
at org.springframework.boot.actuate.endpoint.invoke.reflect.ReflectiveOperationInvoker.invoke(ReflectiveOperationInvoker.java:76)
at org.springframework.boot.actuate.endpoint.annotation.AbstractDiscoveredOperation.invoke(AbstractDiscoveredOperation.java:61)
at org.springframework.boot.actuate.endpoint.jmx.EndpointMBean.invoke(EndpointMBean.java:126)
at org.springframework.boot.actuate.endpoint.jmx.EndpointMBean.invoke(EndpointMBean.java:99)
at java.management/com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:809)
at java.management/com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
at java.management.rmi/javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1466)
at java.management.rmi/javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1307)
at java.management.rmi/javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1399)
at java.management.rmi/javax.management.remote.rmi.RMIConnectionImpl.invoke(RMIConnectionImpl.java:827)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at java.rmi/sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:359)
at java.rmi/sun.rmi.transport.Transport$1.run(Transport.java:200)
at java.rmi/sun.rmi.transport.Transport$1.run(Transport.java:197)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.rmi/sun.rmi.transport.Transport.serviceCall(Transport.java:196)
at java.rmi/sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:562)
at java.rmi/sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:796)
at java.rmi/sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(TCPTransport.java:677)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.rmi/sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:676)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:834)}
)