How to prevent application startup fail in case if mail server unavailable

my application has following gradle depenency:

 compile "org.springframework.boot:spring-boot-starter-mail"

I use mail server available in my network and for me it works fine.

But in another network it doesn't work and application doesn't start:

20.11.17 20:27:15.895 [main] ERROR o.s.boot.SpringApplication - Application startup failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.boot.autoconfigure.mail.MailSenderValidatorAutoConfiguration': Invocation of init method failed; nested exception is java.lang.IllegalStateException: Mail server is not available
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor.postProcessBeforeInitialization(InitDestroyAnnotationBeanPostProcessor.java:137)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization(AbstractAutowireCapableBeanFactory.java:409)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1620)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:761)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:867)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:303)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107)
    at my.Application.main(Application.java:12)
Caused by: java.lang.IllegalStateException: Mail server is not available
    at org.springframework.boot.autoconfigure.mail.MailSenderValidatorAutoConfiguration.validateConnection(MailSenderValidatorAutoConfiguration.java:55)
    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 org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleElement.invoke(InitDestroyAnnotationBeanPostProcessor.java:366)
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleMetadata.invokeInitMethods(InitDestroyAnnotationBeanPostProcessor.java:311)
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor.postProcessBeforeInitialization(InitDestroyAnnotationBeanPostProcessor.java:134)
    ... 18 common frames omitted
Caused by: com.sun.mail.util.MailConnectException: Couldn't connect to host, port: mail.universe.dart.spbqqqq, 25; timeout -1
    at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:2118)
    at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:712)
    at javax.mail.Service.connect(Service.java:366)
    at org.springframework.mail.javamail.JavaMailSenderImpl.connectTransport(JavaMailSenderImpl.java:501)
    at org.springframework.mail.javamail.JavaMailSenderImpl.testConnection(JavaMailSenderImpl.java:382)
    at org.springframework.boot.autoconfigure.mail.MailSenderValidatorAutoConfiguration.validateConnection(MailSenderValidatorAutoConfiguration.java:52)
    ... 25 common frames omitted
Caused by: java.net.UnknownHostException: my.mail.server
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:184)
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:589)
    at java.net.Socket.connect(Socket.java:538)
    at com.sun.mail.util.SocketFetcher.createSocket(SocketFetcher.java:331)
    at com.sun.mail.util.SocketFetcher.getSocket(SocketFetcher.java:238)
    at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:2084)
    ... 30 common frames omitted

Can I make that this exception doesn't affect application startup ?

P.S.

I tried to write:

@Configuration
@AutoConfigureAfter({MailSenderAutoConfiguration.class})
@ConditionalOnProperty(
        prefix = "spring.mail",
        value = {"test-connection"}
)
@ConditionalOnSingleCandidate(JavaMailSenderImpl.class)
public class MailSenderValidatorAutoConfiguration {
    private Logger logger = LoggerFactory.getLogger(MailSenderValidatorAutoConfiguration.class);

    private final JavaMailSenderImpl mailSender;

    public MailSenderValidatorAutoConfiguration(JavaMailSenderImpl mailSender) {
        this.mailSender = mailSender;
    }

    @PostConstruct
    public void validateConnection() {
        try {
            this.mailSender.testConnection();
        } catch (MessagingException var2) {
            logger.warn("Mail server is not available", var2);
        }
    }
}

but this code is not invoked.

Then I added

@Bean
public MailSenderValidatorAutoConfiguration mailSenderValidatorAutoConfiguration(JavaMailSenderImpl javaMailSender){
    return new MailSenderValidatorAutoConfiguration(javaMailSender);
}

And my code is invoked but anyway application wasn't started

Solution

Create two application.properties file. For example application-local.properties and application-nomailserver.properties under src/main/resources folder of the project.
In application-nomailserver.properties put a property like spring.autoconfigure.exclude= <Fully qualified class name you want to exclude >
Now when you want to start your application in your local, you can start with profile local for example.

java -Dspring.profiles.active=local -jar YourJarName

when running in some other machine where you don't have mail server

java -Dspring.profiles.active=nomailserver -jar YourJarName