As mentioned earlier, the out-the-box mail functionality is just the PHP mail() function. The benefit to using this function is that many servers have it pre-configured to allow you to send emails very easily. The drawback is that the implementation of this function differs greatly from server to server. This can sometimes leads to problems, such as emails not being properly sent out but not provide any clues that it didn't in fact work.
With this in mind, we created the Swift Mailer module. This module lets you override the default mail() function and send all emails via an SMTP email server.
For more information about the module, see the module's online documentation.