It's pretty simple, actually. Here is some sample code I used in one of our custom features. I built this by examining other email code throughout the mojoPortal source.

Using mojoPortal.Net;
Using mojoPortal.Web;

            SmtpSettings smtpSettings = SiteUtils.GetSmtpSettings();
            foreach (string email in myEmails)
            {
               EmailMessageTask messageTask = new EmailMessageTask(smtpSettings);

               messageTask.EmailFrom = siteSettings.DefaultEmailFromAddress;
               messageTask.EmailTo = email;
               messageTask.Subject = mySubject;
               messageTask.TextBody = myMessage;
               messageTask.SiteGuid = siteSettings.SiteGuid;
               messageTask.QueueTask();
            }
            WebTaskManager.StartOrResumeTasks();
 

You can also send email directly without a task. For just about anything you might need to do in a custom feature you can find example code in existing features that does something similar. For example to find code for sending email you could look at the code in the Contact Form feature.

Hope that helps,

Joe