class file for javax.mail.internet.MimeMessage not found

It appears you are missing a dependency on javax.mail.

Try adding this to your Maven dependencies.

<dependency>
   <groupId>javax.mail</groupId>
   <artifactId>mail</artifactId>
   <version>1.4.7</version>
</dependency>

bparry's answer still hold. But you should consider replacing it with jakarta.mail instead.

In addition, replace every instance of javax.mail with jakarta.mail in your codebase.