This plugin reconfigures the wp_mail() function to use SMTP instead of mail() and creates an options page that allows you to specify various options.
You can set the following options:
Specify the from name and email address for outgoing email. Choose to send mail by SMTP or PHP's mail() function. Specify an SMTP host (defaults to localhost). Specify an SMTP port (defaults to 25). Choose SSL / TLS encryption (not the same as STARTTLS). Choose to use SMTP authentication or not (defaults to not). Specify an SMTP username and password.