我试着按照以下教程：
http://www.edumobile.org/android/send-email-on-button-click-without-email-chooser/
我添加了库并添加了类SMTPAuthenticator.java和Mail.java，在我将代码添加到我的主要活动之前，我运行了项目，但是我遇到了以下错误：
:app:transformClassesWithDexForDebug
UNEXPECTED TOP-LEVEL EXCEPTION:
com.android.dex.DexIndexOverflowException: method ID not in [0, 0xffff]: 65536
at com.android.dx.merge.DexMerger$6.updateIndex(DexMerger.java:484)
at com.android.dx.merge.DexMerger$IdMerger.mergeSorted(DexMerger.java:261)
at com.android.dx.merge.DexMerger.mergeMethodIds(DexMerger.java:473)
at com.android.dx.merge.DexMerger.mergeDexes(DexMerger.java:161)
at com.android.dx.merge.DexMerger.merge(DexMerger.java:188)
at com.android.dx.command.dexer.Main.mergeLibraryDexBuffers(Main.java:504)
at com.android.dx.command.dexer.Main.runMonoDex(Main.java:334)
at com.android.dx.command.dexer.Main.run(Main.java:277)
at com.android.dx.command.dexer.Main.main(Main.java:245)
at com.android.dx.command.Main.main(Main.java:106)
FAILED
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':app:transformClassesWithDexForDebug'.
> com.android.build.api.transform.TransformException: com.android.ide.common.process.ProcessException: org.gradle.process.internal.ExecException: Process 'command 'C:\Program Files\Java\jdk1.7.0_79\bin\java.exe'' finished with non-zero exit value 2
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
BUILD FAILED
Total time: 1 mins 39.987 secs
有人可以告诉我应该如何解决这个问题。最好的问候。