Fwd: NoClassDefFoundError: javax/mail/Authenticator

[Alan Masters]

I am attempting to send e-mail from Tomcat using an external mail host 
-  mail.btinternet.com.

I have included javax.mail jar in my build path and can see 
javax.mail.Authenticator in this library.

When trying to start up  apache-tomcat-9.0.91 I get 
IllegalStateException: Error starting child

   Caused by: java.lang.NoClassDefFoundError: javax/mail/Authenticator

any help would be appreciated please.