This interface defines a strategy for sending simple mails. Can be
implemented for a variety of mailing systems due to the simple requirements.
For richer functionality like MIME messages, consider JavaMailSender.
Allows for easy testing of clients, as it does not depend on JavaMail's
infrastructure classes: no mocking of JavaMail Session or Transport necessary.
Allows for easy testing of clients, as it does not depend on JavaMail's infrastructure classes: no mocking of JavaMail Session or Transport necessary.