Symptoms

When adding a JNDI setting to an email server (specially if you are connecting your instance to Gmail), the following error is displayed:

The mail settings you entered were not valid. Error thrown was: Mail server at location [java:comp/env/mail/GmailSmtpServer] is not of required type javax.mail.Session.

Cause

As explained on Configuring Bamboo to send SMTP Email, you need to ensure that the files mail-X.X.jar and activation-X.X.jar exist only in the <Bamboo_Install>/lib directory.

The error occurs if the files exist both in <Bamboo-Install>/atlassian-bamboo/WEB-INF/lib and <Bamboo_Install>/lib.

Resolution

Removing the duplicate files will solve the problem.

1. Shutdown Bamboo;
2. Delete the <Bamboo_Install>/lib/mail-X.X.jar and <Bamboo_Install>/lib/activation-X.X.jar
3. Restart Bamboo and attempt to reconfigure your mail server again.