Display E-Mail Adresse of anonym visitors in Drupal-comments securely

Visitors post comments and they live sometimes their contact information like email address to get feedback. If you display e-mail spambots will catch them before other visitors. If you dont display, other visitors cannot send feedback. What is the secure anti-spam solution?

Here is what I did:

- email adresse of comment-poster will just partly shown to other anonym visitors (and with a tip to register to see full email)
- email adresse of comment-poster will shown to other registered visitors fully

To do that I need to change Druplas core comment-module and add a couple of php lines.

public_html/modules/comment/comment.tpl.php



    

	
		if($comment->mail) {

			$comment_posters_name = str_replace("Guest ", "", $comment->name);

			$comment_posters_mail = $comment->mail;

			$comment_posters_mail2 = preg_replace("#(.*@..)(.*)#sim", "$1", $comment_posters_mail);
			if($user->uid){

				echo "
E-Mail Addresse of  $comment_posters_name is: $comment_posters_mail
";

			} else {
				echo "
E-Mail Addresse of  $comment_posters_name({$comment_posters_mail2}...) is just for < a href=\"/user/register\">registered users< /a> available!
";

			}

		}

	?>