How do i send and receive emails from Joomla?

Have to be more specific than that.

  1. if you wish to send emails to customers registered in your website, you should utilize somekind of e-newsletter component - http://extensions.joomla.org/extensions/content-sharing/newsletter
  2. If you wish to sent email programmatically, simplest way is by using
    JUtility::sendMail($from, $fromname, $recipient, $subject, $body, $mode, $cc, $bcc, $attachment, $replyto, $replytoname);
  3. if you want so that it is more complex get mailer and configure by yourself

    $mailer =& JFactory::getMailer();
    $mailer->IsHTML(false);
    $mailer->setSubject("Hello World");
    $mailer->setBody("Hello from Joomla");
    $mailer->addRecipient('your@email.com');
    $mailer->AddCustomHeader('X-Header: example');
    $mailer->Send();
    
  4. If you would like your customers to email one another, you might like to use PMS (Private Messages System) http://extensions.joomla.org/extensions/communication/pms. I'd recomment UddeIM, great texting system.