EmailManager.cls

public class EmailManager {
    //public method
    public void sendMail(String address, String subject, String body) {
        //Create an email message object
        Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
        String[] toAddresses = new String[] {address};
        mail.setToAddress(toAddresses);
        mail.setSubject(subject);
        mail.setPlainTextBody(body);
        //Pass this email message to the built-in sendMail method of the Messaging class
        Messaging.SendEmailResult[] results = Messaging.sendEmail(
                new Messaging.SingleEmailMessage[] { mail }
        );

        //Call a helper method to inspect the returned result
        //This helper method inspects the results of the email send call and is called by sendMail()
        inspectResults(results);
    }

    //Helper method
    private static Boolean inspectResults(Messaging.SendEmailResult[] results) {
        Boolean sendResult = true;

        //sendEmail returns an array of result objects.
        //Iterate through the list to inspect results.
        //In this class, the methods sent only one email,
        //so we should have only one result.
        for(Messaging.SendEmailResult res : results) {
            if(res.isSuccess()) {
                System.debug('Email sent successfully');
            } else {
                sendResult = false;
                System.debug('The following errors occured: ' + res.getErrors());
            }
        }

        return sendResult;
    }
}