AmbiguousMethodCallException Camel - Mail on Exchange.getMessage()

I am working with camel-mail-starter version 3.12.0

I have configured the route this way:

String from = protocol + "://" + host + ":" + port + "?username=" 
    + username + "&password=" + password + "&delete=" + removeAfterConsuming 
    + "&mail.pop3.starttls.enable=true&debugMode=true";
RouteBuilder emailListener = new RouteBuilder () {
    @Override
    public void configure() throws Exception {
        from (from)
            .process (new EmailProcessor (body, client))
            .log("${exchange.message}");
    }
};

My Processor

public void process(Exchange exchange) throws Exception {
    MailMessage message = exchange.getIn(MailMessage.class);
    MimeMessageParser parser = new MimeMessageParser(
        (IMAPMessage) message.getOriginalMessage()
    );

    try {
        parser.parse();
    } catch (Exception e) {
        ApplicationException applicationException = new ApplicationException(
            e.getStackTrace(), 
            Collections.singletonMap("process", " Inside camel mail"), 
            getClass(), "33"
        );
        applicationException.notifyViaEmail();
    }
}

When I run this, I get the following exception

Caused by: org.apache.camel.component.bean.AmbiguousMethodCallException: Ambiguous method invocations possible: [public abstract org.apache.camel.Message org.apache.camel.Exchange.getMessage(), public abstract java.lang.Object org.apache.camel.Exchange.getMessage(java.lang.Class)] on the exchange: Exchange[166D4FAD964C49D-0000000000000000]

I don't know what I am doing wrong

Your mistake is in the simple language expression used in the log EIP, indeed the expression ${exchange.message} asks Camel to call dynamically the method getMessage on the current exchange but as mentioned in the error message, there are 2 existing methods called getMessage in Exchange which are getMessage() and getMessage(java.lang.Class) and Camel has no way to know which one to call which causes this specific exception.

I don't know what you wanted to log but if it is the body of your message the expected expression is rather ${body}. Please refer to the doc about the simple language for more details.