Error in test configuration by sending test email

After putting the smtp server (sendgrid) ,smtp authentication and port 25 then test the configuration by sending the test email. I get the error below.. I tried different configuration combinations but still get the same error. The smtp server is working when used by other servers.  

Test configuration
ERROR
A problem occurred while processing the request. Please check our bug tracker to see if a similar problem has already been reported. If it is already reported, please vote and put a comment on it to let us gauge the impact of the problem. If you think this is a new issue, please file a new issue. When you file an issue, make sure to add the entire stack trace, along with the version of Jenkins and relevant plugins. The users list might be also useful in understanding what has happened.
Stack trace
java.lang.NullPointerException
at hudson.util.Secret$1.convert(Secret.java:306)
at hudson.util.Secret$1.convert(Secret.java:304)
at org.kohsuke.stapler.AnnotationHandler.convert(AnnotationHandler.java:66)
at org.kohsuke.stapler.QueryParameter$HandlerImpl.parse(QueryParameter.java:74)
at org.kohsuke.stapler.QueryParameter$HandlerImpl.parse(QueryParameter.java:62)
at org.kohsuke.stapler.AnnotationHandler.handle(AnnotationHandler.java:91)
at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:204)
at org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:145)
at org.kohsuke.stapler.MetaClass$11.doDispatch(MetaClass.java:535)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:58)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:747)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:878)
at org.kohsuke.stapler.MetaClass$4.doDispatch(MetaClass.java:280)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:58)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:747)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:878)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:676)
at org.kohsuke.stapler.Stapler.service(Stapler.java:238)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:873)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1623)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:154)
at jenkins.telemetry.impl.UserLanguages$AcceptLanguageFilter.doFilter(UserLanguages.java:128)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:151)
at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:157)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:99)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
at hudson.security.UnwrapSecurityExceptionFilter.doFilter(UnwrapSecurityExceptionFilter.java:51)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at jenkins.security.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:117)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.ui.rememberme.RememberMeProcessingFilter.doFilter(RememberMeProcessingFilter.java:142)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:271)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at jenkins.security.BasicHeaderProcessor.doFilter(BasicHeaderProcessor.java:93)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:249)
at hudson.security.HttpSessionContextIntegrationFilter2.doFilter(HttpSessionContextIntegrationFilter2.java:67)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:90)
at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:171)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
at org.kohsuke.stapler.compression.CompressionFilter.doFilter(CompressionFilter.java:49)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
at hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:82)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
at org.kohsuke.stapler.DiagnosticThreadNameFilter.doFilter(DiagnosticThreadNameFilter.java:30)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:540)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:146)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:524)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:257)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1700)
at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:255)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1345)
at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:203)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:480)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1667)
at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:201)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1247)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:144)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
at org.eclipse.jetty.server.Server.handle(Server.java:505)
at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:370)
at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:267)
at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:305)
at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:103)
at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:117)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.runTask(EatWhatYouKill.java:333)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:310)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.tryProduce(EatWhatYouKill.java:168)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.run(EatWhatYouKill.java:126)
at org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread.run(ReservedThreadExecutor.java:366)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:698)
at org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.run(QueuedThreadPool.java:804)
at java.lang.Thread.run(Unknown Source)