Jenkins email plugin configuration using groovy script throws an error - jenkins

Question

I am trying to configure SMTP on jenkins using the email plugin and groovy script call.
Here is the script I am trying to use:
import jenkins.model.Jenkins
def inst = Jenkins.getInstance()
def emailExt = instance.getDescriptor(
"hudson.plugins.emailext.ExtendedEmailPublisher")
emailExt.setSmtpAuth("username",
"password")
emailExt.setDefaultReplyTo("jenkins#example.com")
emailExt.setSmtpServer("smtp.example.com")
emailExt.setUseSsl(true)
emailExt.setSmtpPort("587")
emailExt.setCharset("utf-8")
emailExt.setDefaultRecipients("someone#example.com")
emailExt.save()
When I try to run it using the script console on jenkins, Here is the error I get:
Result
groovy.lang.MissingPropertyException: No such property: instance for class: Script1
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.unwrap(ScriptBytecodeAdapter.java:53)
at org.codehaus.groovy.runtime.callsite.PogoGetPropertySite.getProperty(PogoGetPropertySite.java:52)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callGroovyObjectGetProperty(AbstractCallSite.java:307)
at Script1.run(Script1.groovy:5)
at groovy.lang.GroovyShell.evaluate(GroovyShell.java:585)
at groovy.lang.GroovyShell.evaluate(GroovyShell.java:623)
at groovy.lang.GroovyShell.evaluate(GroovyShell.java:594)
at hudson.util.RemotingDiagnostics$Script.call(RemotingDiagnostics.java:143)
at hudson.util.RemotingDiagnostics$Script.call(RemotingDiagnostics.java:113)
at hudson.remoting.LocalChannel.call(LocalChannel.java:46)
at hudson.util.RemotingDiagnostics.executeGroovy(RemotingDiagnostics.java:110)
at jenkins.model.Jenkins._doScript(Jenkins.java:4698)
at jenkins.model.Jenkins.doScript(Jenkins.java:4669)
at java.base/java.lang.invoke.MethodHandle.invokeWithArguments(MethodHandle.java:710)
at org.kohsuke.stapler.Function$MethodFunction.invoke(Function.java:393)
at org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:405)
at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:208)
at org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:141)
at org.kohsuke.stapler.MetaClass$11.doDispatch(MetaClass.java:536)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:58)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:766)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:898)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:694)
at org.kohsuke.stapler.Stapler.service(Stapler.java:240)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:799)
at org.eclipse.jetty.servlet.ServletHandler$ChainEnd.doFilter(ServletHandler.java:1626)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:156)
Any help is super appreciated!