Also for completeness, the Jenkins JCasC configuration section as currently (and previously) used:

extendedEmailPublisher:
adminRequiredForTemplateTesting: false
allowUnregisteredEnabled: false
charset: "UTF-8"
debugMode: false
defaultBody: " - Build # - :\r\n\r\nCheck console output at to view the results."
defaultContentType: "text/plain"
defaultSubject: " - Build # - !"
maxAttachmentSize: -1
maxAttachmentSizeMb: 0
precedenceBulk: false
smtpServer: "${MF_SMTP_SERVER}"
useSsl: false
watchingEnabled: false

Yes, there have been changes, 2.72 is the first to actually support JCasC. I will look at the trace.

Looks like it might be as simple as changing your "extendedEmailPublisher:" to "email-ext:"

I did actually test that a few minutes ago, and got another stack trace as below.

Do you have idea what options are allowed now, changes since the original working configs?

2020-08-04 15:22:40.194+0000 [id=29] SEVERE jenkins.InitReactorRunner$1#onTaskFailed: Failed ConfigurationAsCode.init
io.jenkins.plugins.casc.ConfiguratorException: 'useSsl' is deprecated
at io.jenkins.plugins.casc.BaseConfigurator.configure(BaseConfigurator.java:321)
at io.jenkins.plugins.casc.BaseConfigurator.check(BaseConfigurator.java:287)
at io.jenkins.plugins.casc.BaseConfigurator.configure(BaseConfigurator.java:351)
at io.jenkins.plugins.casc.BaseConfigurator.check(BaseConfigurator.java:287)
at io.jenkins.plugins.casc.ConfigurationAsCode.lambda$checkWith$8(ConfigurationAsCode.java:755)
at io.jenkins.plugins.casc.ConfigurationAsCode.invokeWith(ConfigurationAsCode.java:691)
Caused: io.jenkins.plugins.casc.ConfiguratorException: unclassified: error configuring 'unclassified' with class io.jenkins.plugins.casc.impl.configurators.GlobalConfigurationCategoryConfigurator configurator
at io.jenkins.plugins.casc.ConfigurationAsCode.invokeWith(ConfigurationAsCode.java:697)
at io.jenkins.plugins.casc.ConfigurationAsCode.checkWith(ConfigurationAsCode.java:755)
at io.jenkins.plugins.casc.ConfigurationAsCode.configureWith(ConfigurationAsCode.java:740)
at io.jenkins.plugins.casc.ConfigurationAsCode.configureWith(ConfigurationAsCode.java:616)
at io.jenkins.plugins.casc.ConfigurationAsCode.configure(ConfigurationAsCode.java:298)
at io.jenkins.plugins.casc.ConfigurationAsCode.init(ConfigurationAsCode.java:290)
Caused: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at hudson.init.TaskMethodFinder.invoke(TaskMethodFinder.java:104)
Caused: java.lang.Error
at hudson.init.TaskMethodFinder.invoke(TaskMethodFinder.java:110)
at hudson.init.TaskMethodFinder$TaskImpl.run(TaskMethodFinder.java:175)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:296)
at jenkins.model.Jenkins$5.runTask(Jenkins.java:1131)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:214)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:117)
at jenkins.security.ImpersonatingExecutorService$1.run(ImpersonatingExecutorService.java:59)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
2020-08-04 15:22:40.197+0000 [id=20] SEVERE hudson.util.BootFailure#publish: Failed to initialize Jenkins
io.jenkins.plugins.casc.ConfiguratorException: 'useSsl' is deprecated
at io.jenkins.plugins.casc.BaseConfigurator.configure(BaseConfigurator.java:321)
at io.jenkins.plugins.casc.BaseConfigurator.check(BaseConfigurator.java:287)
at io.jenkins.plugins.casc.BaseConfigurator.configure(BaseConfigurator.java:351)
at io.jenkins.plugins.casc.BaseConfigurator.check(BaseConfigurator.java:287)
at io.jenkins.plugins.casc.ConfigurationAsCode.lambda$checkWith$8(ConfigurationAsCode.java:755)
at io.jenkins.plugins.casc.ConfigurationAsCode.invokeWith(ConfigurationAsCode.java:691)
Caused: io.jenkins.plugins.casc.ConfiguratorException: unclassified: error configuring 'unclassified' with class io.jenkins.plugins.casc.impl.configurators.GlobalConfigurationCategoryConfigurator configurator
at io.jenkins.plugins.casc.ConfigurationAsCode.invokeWith(ConfigurationAsCode.java:697)
at io.jenkins.plugins.casc.ConfigurationAsCode.checkWith(ConfigurationAsCode.java:755)
at io.jenkins.plugins.casc.ConfigurationAsCode.configureWith(ConfigurationAsCode.java:740)
at io.jenkins.plugins.casc.ConfigurationAsCode.configureWith(ConfigurationAsCode.java:616)
at io.jenkins.plugins.casc.ConfigurationAsCode.configure(ConfigurationAsCode.java:298)
at io.jenkins.plugins.casc.ConfigurationAsCode.init(ConfigurationAsCode.java:290)
Caused: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at hudson.init.TaskMethodFinder.invoke(TaskMethodFinder.java:104)
Caused: java.lang.Error
at hudson.init.TaskMethodFinder.invoke(TaskMethodFinder.java:110)
at hudson.init.TaskMethodFinder$TaskImpl.run(TaskMethodFinder.java:175)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:296)
at jenkins.model.Jenkins$5.runTask(Jenkins.java:1131)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:214)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:117)
at jenkins.security.ImpersonatingExecutorService$1.run(ImpersonatingExecutorService.java:59)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Caused: org.jvnet.hudson.reactor.ReactorException
at org.jvnet.hudson.reactor.Reactor.execute(Reactor.java:282)
at jenkins.InitReactorRunner.run(InitReactorRunner.java:50)
at jenkins.model.Jenkins.executeReactor(Jenkins.java:1164)
at jenkins.model.Jenkins.<init>(Jenkins.java:964)
at hudson.model.Hudson.<init>(Hudson.java:85)
at hudson.model.Hudson.<init>(Hudson.java:81)
at hudson.WebAppMain$3.run(WebAppMain.java:262)
Caused: hudson.util.HudsonFailedToLoad
at hudson.WebAppMain$3.run(WebAppMain.java:279)
2020-08-04 15:22:40.210+0000 [id=20] INFO jenkins.model.Jenkins#cleanUp: Stopping Jenkins
2020-08-04 15:22:40.252+0000 [id=20] INFO jenkins.model.Jenkins$18#onAttained: Started termination
2020-08-04 15:22:40.274+0000 [id=20] INFO jenkins.model.Jenkins$18#onAttained: Completed termination
2020-08-04 15:22:40.275+0000 [id=20] INFO jenkins.model.Jenkins#_cleanUpDisconnectComputers: Starting node disconnection
2020-08-04 15:22:40.279+0000 [id=20] INFO jenkins.model.Jenkins#_cleanUpShutdownPluginManager: Stopping plugin manager
2020-08-04 15:22:40.944+0000 [id=20] INFO jenkins.model.Jenkins#_cleanUpPersistQueue: Persisting build queue
2020-08-04 15:22:40.970+0000 [id=20] INFO jenkins.model.Jenkins#_cleanUpAwaitDisconnects: Waiting for node disconnection completion
2020-08-04 15:22:40.971+0000 [id=20] INFO jenkins.model.Jenkins#cleanUp: Jenkins stopped

alecharp Any help here? I am not super familiar with JCasC

Could you make fix the indentation (welcome to the YAML world (sarcasm)) on the configuration example you provided?

From what I understand of the stack-trace, it seems that the useSsl is being read by the unclassified category. It seems odd.

Please see the example on the plugin repository: https://github.com/jenkinsci/email-ext-plugin/blob/master/src/test/resources/configuration-as-code.yml

I'll look at the provided config snippet and try to make it work.   It appears there is a serious change in the configuration block, since it worked with the previous indentation.

It might be a good idea to let people know this appears to be a breaking change for those using JCasC...

alecharp slide_o_mix Looking at your configuration this is very different from what was working with the last version of email-ext.  Is there any description of all those config items, and which are required?  Especially when talking of new levels, like "addAccount" and "mailAccount".