Grails 3 mail: Must issue a STARTTLS command first - grails

Question

I know this question has been asked many times in many different places, but for some reason, I can't seem to get it to work. I realize what the issue is, I just can't seem to figure out the yaml syntax or something simple like that.
I'm using Grails 3 with the "mail" plugin (2.0.0.RC6).
Here is a snippet of my application.yml:
grails:
serverURL: <url>
mail:
host: <host>
port: 587
username: <username>
password: <password>
props:
? "mail.smtp.auth" : true
? "mail.smtp.starttls.enable" : true
? "mail.smtp.starttls.required" : true
? "mail.smtp.socketFactory.class" : "javax.net.ssl.SSLSocketFactory"
? "mail.smtp.socketFactory.fallback" : false
? "mail.smtp.port" : 587
I've tried many combinations of quotes with no luck. The ? instead of a - indicates a map, which is what I want I think.
Here is the specific error message if it helps:
Failed messages: com.sun.mail.smtp.SMTPSendFailedException: 530 5.7.0 Must issue a STARTTLS command first
. Stacktrace follows:
java.lang.reflect.InvocationTargetException: null
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.springframework.mail.MailSendException: Failed messages: com.sun.mail.smtp.SMTPSendFailedException: 530 5.7.0 Must issue a STARTTLS command first
at grails.plugins.mail.MailMessageBuilder.sendMessage(MailMessageBuilder.groovy:130)
at grails.plugins.mail.MailService.sendMail(MailService.groovy:53)
at grails.plugins.mail.MailService.sendMail(MailService.groovy:57)
at website.UserController.register(UserController.groovy:60)
... 3 common frames omitted
This is a custom mail server running Postfix (first time setting it up). I am able to connect to it and send mail with Thunderbird. Thunderbird is using STARTTLS and port 587 to connect. As far as I know, I haven't been able to do just SSL/TLS.
update:
I've removed the factory config and fixed the yaml map stuff. Now I'm getting another error.
grails:
serverURL: https://test.neonorb.com
mail:
host: test.neonorb.com
port: 587
username: neonorb
password: pass
props:
mail.smtp.starttls.enable: true
mail.smtp.port: 587
Here is the exception:
unable to find valid certification path to requested target. Stacktrace follows:
java.lang.reflect.InvocationTargetException: null
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.springframework.mail.MailSendException: Mail server connection failed; nested exception is javax.mail.MessagingException: Could not convert socket to TLS;
nested exception is:
javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target. Failed messages: javax.mail.MessagingException: Could not convert socket to TLS;
nested exception is:
javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at grails.plugins.mail.MailMessageBuilder.sendMessage(MailMessageBuilder.groovy:130)
at grails.plugins.mail.MailService.sendMail(MailService.groovy:53)
at grails.plugins.mail.MailService.sendMail(MailService.groovy:57)
at website.UserController.register(UserController.groovy:60)
... 3 common frames omitted
Caused by: javax.mail.MessagingException: Could not convert socket to TLS
at com.sun.mail.smtp.SMTPTransport.startTLS(SMTPTransport.java:2046)
at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:711)
at javax.mail.Service.connect(Service.java:366)
... 7 common frames omitted
Caused by: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at com.sun.mail.util.SocketFetcher.configureSSLSocket(SocketFetcher.java:598)
at com.sun.mail.util.SocketFetcher.startTLS(SocketFetcher.java:525)
at com.sun.mail.smtp.SMTPTransport.startTLS(SMTPTransport.java:2041)
... 9 common frames omitted
Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
... 12 common frames omitted
Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:280)
... 12 common frames omitted
According to Google, this is because the certificate is self-signed, and Java doesn't trust it. My certificate is not self-signed, and is made from Let's Encrypt.

Answer 1

Get rid of the socket factory properties, they're long since obsolete.