Source

File: wp-includes/class-pop3.php

function parse_banner ( $server_text ) {
        $outside = true;
        $banner = "";
        $length = strlen($server_text);
        for($count =0; $count < $length; $count++)
        {
            $digit = substr($server_text,$count,1);
            if(!empty($digit))             {
                if( (!$outside) && ($digit != '<') && ($digit != '>') )
                {
                    $banner .= $digit;
                }
                if ($digit == '<')
                {
                    $outside = false;
                }
                if($digit == '>')
                {
                    $outside = true;
                }
            }
        }
        $banner = $this->strip_clf($banner);    // Just in case
        return "<$banner>";
    }