Can't Get Drupal to Send Mail

Hello. I've been working with Drupal for a couple weeks, and have a module / feature that has me totally stumped. Every time I try to get the mail features going, I end up bringing down the entire site.

Here's what I've tried:

Downloaded and installed smtp-6.x-1-beta. Downloaded and installed phpmailer-6.x-2.1. I extract the PHP module inside the smtp folder (I've also tried right off the modules folder). Then I go in to the modules page and turn them on. Then, I go to the SMTP configuration area (where you enter sender name, password, etc) - once I click to Save, it tries to send a test and I get errors.

First error I get: Fatal error: require_once() [function.require]: Failed opening required 'sites/all/modules/smtp/phpmailer/class.phpmailer.php' (include_path='.:/usr/share/php:/usr/share/pear') in /etc/drupal/6/sites/all/modules/smtp/smtp.module on line 246

So, I figure it's missing this file "class.phpmailer.php". I keep reading (on support forums here, etc.) that I need to install the php class files. But I don't see these files in any of the zip files, and don't think I'm looking in the right place for them. So, I download the files from the only place I can find them from a google search. I then put them in the smtp/phpmailer folder.

Then, I get this error and the site goes down: warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, 'phpmailer_preview_access' was given in /usr/share/drupal6/includes/menu.inc on line 452.

I get the site back up by deleting the modules\smtp folder. But, obviously, mail still doesn't work.

My guess is I'm not getting the right "php class files", or not putting them in the right folder location or something. Can anyone help? Thanks.