Cant get into servers!

[TatiestEwe2200]

when i tried to join this server: server ip: erdbeerbaerlp.de:24259 or any other server it would tell me that it is unable to authenticate using ULPP. Here is what it said: Started alive keeper
Server is using ULPP version 1
javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at sun.security.ssl.Alert.createSSLException(Unknown Source)
at sun.security.ssl.TransportContext.fatal(Unknown Source)
at sun.security.ssl.TransportContext.fatal(Unknown Source)
at sun.security.ssl.TransportContext.fatal(Unknown Source)
at sun.security.ssl.CertificateMessage$T12CertificateConsumer.checkServerCerts(Unknown Source)
at sun.security.ssl.CertificateMessage$T12CertificateConsumer.onCertificate(Unknown Source)
at sun.security.ssl.CertificateMessage$T12CertificateConsumer.consume(Unknown Source)
at sun.security.ssl.SSLHandshake.consume(Unknown Source)
at sun.security.ssl.HandshakeContext.dispatch(Unknown Source)
at sun.security.ssl.HandshakeContext.dispatch(Unknown Source)
at sun.security.ssl.TransportContext.dispatch(Unknown Source)
at sun.security.ssl.SSLTransport.decode(Unknown Source)
at sun.security.ssl.SSLSocketImpl.decode(Unknown Source)
at sun.security.ssl.SSLSocketImpl.readHandshakeRecord(Unknown Source)
at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
at sun.net.www.protocol.https.HttpsClient.afterConnect(Unknown Source)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getOutputStream0(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getOutputStream(Unknown Source)
at sun.net.www.protocol.https.HttpsURLConnectionImpl.getOutputStream(Unknown Source)
at net.minecraft.src.NetULPP1ClientHandler.getPostCode(NetULPP1ClientHandler.java:39)
at net.minecraft.src.NetULPP1ClientHandler.a(NetULPP1ClientHandler.java:69)
at gy.a(NetClientHandler.java:57)
at hp.a(Packet1Login.java:37)
at ii.a(NetworkManager.java:212)
at mn.g(GuiConnecting.java:19)
at net.minecraft.client.Minecraft.i(Minecraft.java:864)
at net.minecraft.client.Minecraft.run(Minecraft.java:519)
at java.lang.Thread.run(Unknown Source)
Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at sun.security.validator.PKIXValidator.doBuild(Unknown Source)
at sun.security.validator.PKIXValidator.engineValidate(Unknown Source)
at sun.security.validator.Validator.validate(Unknown Source)
at sun.security.ssl.X509TrustManagerImpl.validate(Unknown Source)
at sun.security.ssl.X509TrustManagerImpl.checkTrusted(Unknown Source)
at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(Unknown Source)
... 26 more
Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at sun.security.provider.certpath.SunCertPathBuilder.build(Unknown Source)
at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(Unknown Source)
at java.security.cert.CertPathBuilder.build(Unknown Source)
... 32 more
Loading texture skin:///TattiestEwe2200
Player count: 1
Network closed: Got kicked
Stopped alive keeper
AL lib: (EE) MMDevApiProc: WaitForSingleObjectEx error: 0x102
AL lib: (EE) MMDevApiProc: WaitForSingleObjectEx error: 0x102
AL lib: (EE) MMDevApiProc: WaitForSingleObjectEx error: 0x102
AL lib: (EE) MMDevApiProc: WaitForSingleObjectEx error: 0x102

[5GameMaker]

Closing due to #34