Index: invite.module
===================================================================
--- invite.module	(revision 2284)
+++ invite.module	(working copy)
@@ -440,6 +440,13 @@
     '#description' => t('Choose whether users should be able to customize the subject.'),
     '#default_value' => variable_get('invite_subject_editable', FALSE),
   );
+  $form['email']['invite_email_format_html'] = array(
+    '#type' => 'radios',
+    '#title' => t('Email format'),
+    '#description' => t('Choose the format you prefer for your invitation emails.'),
+    '#options' => array(t('Plain text'), t('HTML')),
+    '#default_value' => variable_get('invite_email_format_html', FALSE),
+  );  
   $form['email']['invite_default_mail_template'] = array(
     '#type' => 'textarea',
     '#title' => t('Mail template'),
@@ -1066,7 +1073,13 @@
     $headers['Reply-To'] = $reply_to;
   }
 
-  if (!($success = drupal_mail('invite-mail', $recipient, $subject, wordwrap($body, 72), $from, $headers))) {
+  if (module_exists('mimemail') && variable_get('invite_email_format_html', FALSE)) {
+    $success = mimemail($from, $recipient, $subject, wordwrap($body, 72), FALSE, $headers);
+  } else {
+    $success = drupal_mail('invite-mail', $recipient, $subject, wordwrap($body, 72), $from, $headers);
+  }
+  
+  if (!$success) {
     static $error_shown = FALSE;
     if (!$error_shown) {
       drupal_set_message(t('Problems occurred while sending the invitation(s). Please contact the site administrator.'), 'error');