emails are not sent, if GNU mail.jar is on CLASS_PATH

Steps needed to reproduce the behaviour:

1. Install Tomcat provided in packaged by Linux.
2. Place on CLASS_PATH mail-1.1.2 from GNU JavaMail.
3. Deploy JIRA WAR.
4. Configure SMTP integration in JIRA.
5. Attempt to sent email for e.g. from the admin > Services > SMTP.

   An error has occurred with sending the test email:
   com.atlassian.mail.MailException: javax.mail.NoSuchProviderException: smtp
   at com.atlassian.mail.server.impl.SMTPMailServerImpl.send(SMTPMailServerImpl.java:191)
   at com.atlassian.jira.web.action.admin.mail.SendTestMail.doExecute(SendTestMail.java:91)
   at webwork.action.ActionSupport.execute(ActionSupport.java:165)
   at com.atlassian.jira.action.JiraActionSupport.execute(JiraActionSupport.java:54)
   at webwork.dispatcher.GenericDispatcher.executeAction(GenericDispatcher.java:139)
   ...
   Caused by: javax.mail.NoSuchProviderException: smtp
   at javax.mail.Session.getService(Session.java:794)
   at javax.mail.Session.getTransport(Session.java:718)
   at javax.mail.Session.getTransport(Session.java:661)
   at javax.mail.Session.getTransport(Session.java:641)
   at alt.javax.mail.SessionImpl.getTransport(SessionImpl.java:77)
   at com.atlassian.mail.server.impl.SMTPMailServerImpl.send(SMTPMailServerImpl.java:177)
   ... 111 more
   
   DEBUG: getProvider() returning javax.mail.Provider[TRANSPORT,smtp,gnu.mail.providers.smtp.SMTPTransport,nferrier@tapsellferrier.co.uk]
   java.lang.NoSuchMethodException: gnu.mail.providers.smtp.SMTPTransport.<init>(javax.mail.Session, javax.mail.URLName)
   at java.lang.Class.getConstructor0(Unknown Source)
   at java.lang.Class.getConstructor(Unknown Source)
   

Possible work around is listed in our documentation.

To prevent any conflicts, check your application server's lib/ directory:

• If the application server already contains mail-1.4.1.jar and activation-1.1.1.jar, then just remove WEB-INF/lib/mail-1.4.1.jar and WEB-INF/lib/activation-1.1.1.jar from the JIRA webapp.
• If the application server does not contain mail-1.4.1.jar and activation-1.1.1.jar, then move JIRA's WEB-INF/lib/mail-1.4.1.jar and WEB-INF/lib/activation-1.1.1.jar into the application server's lib/ directory

http://confluence.atlassian.com/display/JIRA/Configuring+JIRA+to+Send+SMTP+Mail#ConfiguringJIRAtoSendSMTPMail-MovetheJavaMailClasses