public void startMailTransaction() throws IllegalStateException {
        if (this.messageHandler != null) {
            throw new IllegalStateException("Mail transaction is already in progress");
        }
        this.messageHandler = this.server.getMessageHandlerFactory().create(this);
    }
Starts a mail transaction by creating a new message handler.

@throws IllegalStateException if a mail transaction is already in progress
src/main/java/de/gessnerfl/fakesmtp/smtp/server/Session.java