A small wrapper class to send emails - Used as a sample as a hard to test implementation(we cannot replace the SmtpClient itself)

MailSenderService.cs

    /// <summary>
    /// Implementation of the mail sender service.
    /// </summary>
    public class MailSenderService
    {
        /// <summary>
        /// Sends the mail using the specified options.
        /// </summary>
        /// <param name="mail">The mail.</param>
        /// <param name="mailOptions">The mail options.</param>
        public void SendMail(Mail mail, MailOptions mailOptions)
        {
            SmtpClient client = new SmtpClient();
            if (mailOptions.SaveToFile)
            {
                client.DeliveryMethod = SmtpDeliveryMethod.SpecifiedPickupDirectory;
                client.PickupDirectoryLocation = mailOptions.FilePath;
            }
                    
            client.Send(mail.GetMailMessage());
            Trace.TraceInformation("Send mail successfully with subject : '{0}' from '{1}'.".FormatWith(mail.Subject, mail.FromAddress.Address));
        }
    }