The Plugin does not honor the port selection in the config page.
Selected is 636 yet 389 is used. See the provided log:

Jul 05, 2016 7:14:37 PM FINE org.acegisecurity.ui.AbstractProcessingFilter unsuccessfulAuthentication
Authentication request failed: org.acegisecurity.BadCredentialsException: Failed to retrieve user information for schmidt; nested exception is javax.naming.PartialResultException [Root exception is javax.naming.CommunicationException: simple bind failed: int.iils.de:389 [Root exception is java.net.SocketException: Connection reset]]

Jul 05, 2016 7:14:37 PM FINE hudson.security.AuthenticationProcessingFilter2
Login attempt failed
org.acegisecurity.BadCredentialsException: Failed to retrieve user information for schmidt; nested exception is javax.naming.PartialResultException [Root exception is javax.naming.CommunicationException: simple bind failed: int.iils.de:389 [Root exception is java.net.SocketException: Connection reset]]
at hudson.plugins.active_directory.ActiveDirectoryUnixAuthenticationProvider$1.call(ActiveDirectoryUnixAuthenticationProvider.java:332)
at hudson.plugins.active_directory.ActiveDirectoryUnixAuthenticationProvider$1.call(ActiveDirectoryUnixAuthenticationProvider.java:235)
at com.google.common.cache.LocalCache$LocalManualCache$1.load(LocalCache.java:4767)
at com.google.common.cache.LocalCache$LoadingValueReference.loadFuture(LocalCache.java:3568)
at com.google.common.cache.LocalCache$Segment.loadSync(LocalCache.java:2350)
at com.google.common.cache.LocalCache$Segment.lockedGetOrLoad(LocalCache.java:2313)
at com.google.common.cache.LocalCache$Segment.get(LocalCache.java:2228)
at com.google.common.cache.LocalCache.get(LocalCache.java:3965)
at com.google.common.cache.LocalCache$LocalManualCache.get(LocalCache.java:4764)
at hudson.plugins.active_directory.ActiveDirectoryUnixAuthenticationProvider.retrieveUser(ActiveDirectoryUnixAuthenticationProvider.java:235)
at hudson.plugins.active_directory.ActiveDirectoryUnixAuthenticationProvider.retrieveUser(ActiveDirectoryUnixAuthenticationProvider.java:200)
at hudson.plugins.active_directory.ActiveDirectoryUnixAuthenticationProvider.retrieveUser(ActiveDirectoryUnixAuthenticationProvider.java:142)
at org.acegisecurity.providers.dao.AbstractUserDetailsAuthenticationProvider.authenticate(AbstractUserDetailsAuthenticationProvider.java:122)
at org.acegisecurity.providers.ProviderManager.doAuthentication(ProviderManager.java:200)
at org.acegisecurity.AbstractAuthenticationManager.authenticate(AbstractAuthenticationManager.java:47)
at org.acegisecurity.ui.webapp.AuthenticationProcessingFilter.attemptAuthentication(AuthenticationProcessingFilter.java:74)
at org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:252)
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$1.doFilter(ChainedServletFilter.java:87)
at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:171)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
at org.kohsuke.stapler.compression.CompressionFilter.doFilter(CompressionFilter.java:49)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
at hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:82)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
at org.kohsuke.stapler.DiagnosticThreadNameFilter.doFilter(DiagnosticThreadNameFilter.java:30)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:585)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:553)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:223)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1127)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:515)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1061)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
at org.eclipse.jetty.server.Server.handle(Server.java:499)
at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:311)
at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:257)
at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:544)
at winstone.BoundedExecutorService$1.run(BoundedExecutorService.java:77)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: javax.naming.PartialResultException [Root exception is javax.naming.CommunicationException: simple bind failed: int.iils.de:389 [Root exception is java.net.SocketException: Connection reset]]
at com.sun.jndi.ldap.AbstractLdapNamingEnumeration.hasMoreImpl(AbstractLdapNamingEnumeration.java:237)
at com.sun.jndi.ldap.AbstractLdapNamingEnumeration.hasMore(AbstractLdapNamingEnumeration.java:189)
at hudson.plugins.active_directory.LDAPSearchBuilder.searchOne(LDAPSearchBuilder.java:86)
at hudson.plugins.active_directory.ActiveDirectoryUnixAuthenticationProvider$1.call(ActiveDirectoryUnixAuthenticationProvider.java:309)
... 49 more
Caused by: javax.naming.CommunicationException: simple bind failed: int.iils.de:389 [Root exception is java.net.SocketException: Connection reset]
at com.sun.jndi.ldap.LdapReferralContext.<init>(LdapReferralContext.java:95)
at com.sun.jndi.ldap.LdapReferralException.getReferralContext(LdapReferralException.java:150)
at com.sun.jndi.ldap.AbstractLdapNamingEnumeration.hasMoreReferrals(AbstractLdapNamingEnumeration.java:325)
at com.sun.jndi.ldap.AbstractLdapNamingEnumeration.hasMoreImpl(AbstractLdapNamingEnumeration.java:227)
... 52 more
Caused by: java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(SocketInputStream.java:209)
at java.net.SocketInputStream.read(SocketInputStream.java:141)
at sun.security.ssl.InputRecord.readFully(InputRecord.java:465)
at sun.security.ssl.InputRecord.read(InputRecord.java:503)
at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:973)
at sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1375)
at sun.security.ssl.SSLSocketImpl.writeRecord(SSLSocketImpl.java:747)
at sun.security.ssl.AppOutputStream.write(AppOutputStream.java:123)
at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82)
at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:140)
at com.sun.jndi.ldap.Connection.writeRequest(Connection.java:426)
at com.sun.jndi.ldap.Connection.writeRequest(Connection.java:399)
at com.sun.jndi.ldap.LdapClient.ldapBind(LdapClient.java:359)
at com.sun.jndi.ldap.LdapClient.authenticate(LdapClient.java:214)
at com.sun.jndi.ldap.LdapCtx.connect(LdapCtx.java:2788)
at com.sun.jndi.ldap.LdapCtx.<init>(LdapCtx.java:319)
at com.sun.jndi.ldap.LdapCtxFactory.getUsingURL(LdapCtxFactory.java:192)
at com.sun.jndi.ldap.LdapCtxFactory.getLdapCtxInstance(LdapCtxFactory.java:151)
at com.sun.jndi.url.ldap.ldapURLContextFactory.getObjectInstance(ldapURLContextFactory.java:52)
at javax.naming.spi.NamingManager.getURLObject(NamingManager.java:601)
at javax.naming.spi.NamingManager.processURL(NamingManager.java:381)
at javax.naming.spi.NamingManager.processURLAddrs(NamingManager.java:361)
at javax.naming.spi.NamingManager.getObjectInstance(NamingManager.java:333)
at com.sun.jndi.ldap.LdapReferralContext.<init>(LdapReferralContext.java:114)
... 55 more