Based on http://silverstripe.org/smtpmailer-module/ but as it's outdated and not available on GitHub I created this fork.

silverstripe-smtp automatically sends emails (e.g. from UserForms) to your provider's or host's SMTP server instead of using PHP's built-in mail() function.

silverstripe-smtp replaces the classic SilverStripe Mailer (using the mail() function) with PHPMailer 5.2.22 (https://github.com/PHPMailer/PHPMailer, was http://sourceforge.net/projects/phpmailer/) to send emails via the SMTP protocol to a local or remote SMTP server.

When would you use this module:

• If your provider disabled mail()
• If you have troubles sending emails because of the DNS configuration and the way some mail servers discard emails if the domain names don't match
• If you want to send emails from your local web server without having to install a mail server, using an external SMTP server instead
• If you want to send encrypted emails (using SSL or TLS protocols)
• If you are using Amazon Web Services and would like to utilize the SES (Simple Email Service) which requires throttling and the use of SMTP with authentication over SSL/TLS.

SilverStripe 2.3+

1. Extract the silverstripe-smtp folder into the top level of your site and rename it to smtp
2. Without any configuration, the module is going to connect to the mail server on localhost without authentication
3. If you want to fall back to the classic mailer without uninstalling the module: Edit smtp/_config.php and comment out the set_mailer statement

Configure the module by editing mysite/_config.php and set the following constants:

//Required:
define('SMTPMAILER_SMTP_SERVER_ADDRESS', 'smtp.gmail.com'); //SMTP server address
define('SMTPMAILER_DO_AUTHENTICATE', true); //Turn on SMTP server authentication. Set to false for an anonymous connection
define('SMTPMAILER_USERNAME', '[email protected]'); //SMTP server username, if SMTPAUTH == true
define('SMTPMAILER_PASSWORD', 'bar'); //SMTP server password, if SMTPAUTH == true

//Optional:
define('SMTPMAILER_CHARSET_ENCODING', 'utf-8'); //Email characters encoding, e.g. : 'utf-8' or 'iso-8859-1'
define('SMTPMAILER_USE_SECURE_CONNECTION', 'ssl'); //SMTP encryption method : Set to '', 'tls', or 'ssl'
define('SMTPMAILER_SMTP_SERVER_PORT', 465); //SMTP server port. Set to 25 if no encryption is used, 465 if ssl or tls is activated
define('SMTPMAILER_DEBUG_MESSAGING_LEVEL', 0); //Print debugging informations. 0 = no debuging, 1 = print errors, 2 = print errors and messages, 4 = print full activity
define('SMTPMAILER_LANGUAGE_OF_MESSAGES', 'de'); //Language for messages. Look into smtp/code/vendor/language/ for available languages
define('SMTPMAILER_SEND_DELAY', 2000);//throttling, in milliseconds, can also be 0