Willing to contribute to the repo by adding 1 small feature I need to make work for my case.
https://github.com/jenkinsci/email-ext-plugin/

Is there any step guide how to build it rightly as I see a lot of errors?
I couldn't find any contributing doc & reporting issue is also disabled.

Steps I Tried:
1. forked & cloned into my local box
2. imported as maven project in eclipse
3. tried maven update but it failed with Maven dependency building failures
The error logs in pom file is attached PFA txt file Maven dependency building failures
​4. then tried from command line
mvn clean - it passed
mvn install - it failed (attached screenshot)

Stacktrace:

Running InjectedTest
Tests run: 7, Failures: 0, Errors: 5, Skipped: 0, Time elapsed: 33.263 sec <<< FAILURE! - in InjectedTest
testPluginActive(org.jvnet.hudson.test.PluginAutomaticTestBuilder$OtherTests) Time elapsed: 0.001 sec <<< ERROR!
java.lang.Error: Plugin the.jpl failed to start
at org.jvnet.hudson.test.PluginAutomaticTestBuilder$OtherTests.testPluginActive(PluginAutomaticTestBuilder.java:92)
Caused by: java.io.IOException: No such file: /Users/pooja/Documents/Automation/workspace/open/email-ext-plugin/target/classes

initializationError(org.junit.runner.manipulation.Filter) Time elapsed: 0 sec <<< ERROR!
java.lang.Exception: No tests found matching Method testPluginActive(org.jvnet.hudson.test.PluginAutomaticTestBuilder$OtherTests) from org.junit.internal.requests.ClassRequest@64502326

initializationError(org.junit.runner.manipulation.Filter) Time elapsed: 0.001 sec <<< ERROR!
java.lang.Exception: No runnable methods

initializationError(org.junit.runner.manipulation.Filter) Time elapsed: 0.001 sec <<< ERROR!
java.lang.Exception: No runnable methods

initializationError(org.junit.runner.manipulation.Filter) Time elapsed: 0 sec <<< ERROR!
java.lang.Exception: No runnable methods

Results :

Tests in error:
org.junit.runner.manipulation.Filter.initializationError(org.junit.runner.manipulation.Filter)
Run 1: Filter.initializationError » No tests found matching Method testPluginActive(...
Run 2: Filter.initializationError » No runnable methods
Run 3: Filter.initializationError » No runnable methods
Run 4: Filter.initializationError » No runnable methods

PluginAutomaticTestBuilder$OtherTests.testPluginActive:92 Plugin the.jpl fail...

Tests run: 4, Failures: 0, Errors: 2, Skipped: 0

[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 50.673 s
[INFO] Finished at: 2016-07-21T14:38:07+05:30
[INFO] Final Memory: 37M/821M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-surefire-plugin:2.19.1:test (default-test) on project email-ext: There are test failures.
[ERROR]
[ERROR] Please refer to /Users/pooja/Documents/Automation/workspace/open/email-ext-plugin/target/surefire-reports for the individual test results.
[ERROR] -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-surefire-plugin:2.19.1:test (default-test) on project email-ext: There are test failures.

Please refer to /Users/pooja/Documents/Automation/workspace/open/email-ext-plugin/target/surefire-reports for the individual test results.
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:212)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
at org.apache.maven.cli.MavenCli.execute(MavenCli.java:862)
at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:286)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:197)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
Caused by: org.apache.maven.plugin.MojoFailureException: There are test failures.

Please refer to /Users/pooja/Documents/Automation/workspace/open/email-ext-plugin/target/surefire-reports for the individual test results.
at org.apache.maven.plugin.surefire.SurefireHelper.reportExecution(SurefireHelper.java:91)
at org.apache.maven.plugin.surefire.SurefirePlugin.handleSummary(SurefirePlugin.java:320)
at org.apache.maven.plugin.surefire.AbstractSurefireMojo.executeAfterPreconditionsChecked(AbstractSurefireMojo.java:892)
at org.apache.maven.plugin.surefire.AbstractSurefireMojo.execute(AbstractSurefireMojo.java:755)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:208)
... 20 more
[ERROR]