Index: wp-includes/pluggable.php
===================================================================
--- wp-includes/pluggable.php	(revision 6349)
+++ wp-includes/pluggable.php	(working copy)
@@ -235,7 +235,7 @@
 			$sitename = substr( $sitename, 4 );
 		}
 
-		$from_email = 'wordpress@' . $sitename;
+		$from_email = get_option('admin_email');
 	}
 
 	// Set the from name and email
Index: wp-admin/includes/upgrade.php
===================================================================
--- wp-admin/includes/upgrade.php	(revision 6349)
+++ wp-admin/includes/upgrade.php	(working copy)
@@ -114,7 +114,7 @@
 	$user = new WP_User($user_id);
 	$email = $user->user_email;
 	$name = $user->user_login;
-	$message_headers = 'From: "' . $blog_title . '" <wordpress@' . $_SERVER['SERVER_NAME'] . '>';
+	$message_headers = 'From: "' . $blog_title . '" <'. get_option('admin_email') . '>';
 	$message = sprintf(__("Your new WordPress blog has been successfully set up at:
 
 %1\$s