Error sending mail with Bamboo "NoClassDefFoundError: javax/activation/DataHandler"

[Adrien Ragot _Requirement Yogi_]

When I try to send a test email in the Bamboo 8.1.1 administration, it dislays an exception:

ognl.MethodFailedException: Method "save" failed for object com.atlassian.bamboo.ww2.actions.admin.mail.ConfigureMailServer@58c8309 [java.lang.NoClassDefFoundError: javax/activation/DataHandler]
at ognl.OgnlRuntime.callAppropriateMethod(OgnlRuntime.java:1981)
...
Caused by: java.lang.NoClassDefFoundError: javax/activation/DataHandler
at com.atlassian.mail.server.impl.SMTPMailServerImpl.sendWithMessageId(SMTPMailServerImpl.java:169)
at com.atlassian.mail.server.impl.SMTPMailServerImpl.send(SMTPMailServerImpl.java:159)
at com.atlassian.bamboo.mail.EmailService.sendEmailSynchronously(EmailService.java:115)
at com.atlassian.bamboo.mail.BambooMailer.send(BambooMailer.java:74)
at com.atlassian.bamboo.ww2.actions.admin.mail.ConfigureMailServer.testSMTPServer(ConfigureMailServer.java:130)
at com.atlassian.bamboo.ww2.actions.admin.mail.ConfigureMailServer.save(ConfigureMailServer.java:172)
...
Caused by: java.lang.ClassNotFoundException: javax.activation.DataHandler
at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:471)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:589)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
... 302 more

More metadata:

Version: 8.1.1
Build: 80108
Build Date: 14 Dec 2021

Request information:
Request URL: https://bamboo.___.com/admin/saveMailServer.action
Scheme: https
Server: bamboo.dev.___.com
Port: 443
URI: /admin/saveMailServer.action
Context path:
Servlet path: /admin/saveMailServer.action
Path info:
Query string:

I'm on Java 11.0.11. I have moved the mail-1.6.2 and mail-api-1.5.6 from WEB-INF/lib to /lib, as recommended in the guidelines:

./atlassian-bamboo-8.1.1/lib/javax.mail-1.6.2.jar

./atlassian-bamboo-8.1.1/lib/javax.mail-api-1.5.6.jar

./atlassian-bamboo-8.1.1/atlassian-bamboo/WEB-INF/lib/atlassian-mail-5.0.0.jar

./atlassian-bamboo-8.1.1/atlassian-bamboo/WEB-INF/lib/cloud-compatible-email-validation-1.0.2.jar

 and I've configured the admin to use a JNDI mail, but the same thing happens if I type the email parameters manually into the administraiton.

Can anyone help me?

[Gonchik Tsymzhitov]

Could you replace

javax.mail-1.6.2.jar

 with next version https://mvnrepository.com/artifact/javax.mail/javax.mail-api/1.5.6 ?