Both PHP's native implementation and the function of ericth at NOSPAM dot pennyworth dot com (below) contain an feature/error (usage for SMTP mismatch) which has been solved in my adjustment below.

The error causes a text containing period character(s), when passed through these functions, end up with encoded lines starting with a period character, the first period character on that line will be discarded when it is transported over SMTP.

Solution: add (another) leading '.' to period characters which would end up as first character on a line when encoded.

See http://stackoverflow.com/a/13949483: "This is a dirty artifact of your transport layer... SMTP is the most probable culprit (see the call for caution in the mail function documentation) but there may be other low level mecanisms that behave similarly. For example if you tweaked the sendmail_path setting or use a buggy sendmail program you may experience similar woes."

<?php
define('PHP_QPRINT_MAXL', 75);

function leading_dot_fixed_php_quot_print_encode($str)
{
    $lp = 0;
    $ret = '';
    $hex = "0123456789ABCDEF";
    $length = strlen($str);
    $str_index = 0;
    
    while ($length--) {
        if ((($c = $str[$str_index++]) == "\015") && ($str[$str_index] == "\012") && $length > 0) {
            $ret .= "\015";
            $ret .= $str[$str_index++];
            $length--;
            $lp = 0;
        } else {
            if (ctype_cntrl($c) 
                || (ord($c) == 0x7f) 
                || (ord($c) & 0x80) 
                || ($c == '=') 
                || (($c == ' ') && ($str[$str_index] == "\015")))
            {
                if (($lp += 3) > PHP_QPRINT_MAXL)
                {
                    $ret .= '=';
                    $ret .= "\015";
                    $ret .= "\012";
                    $lp = 3;
                }
                $ret .= '=';
                $ret .= $hex[ord($c) >> 4];
                $ret .= $hex[ord($c) & 0xf];
            } 
            else 
            {
                if ((++$lp) > PHP_QPRINT_MAXL) 
                {
                    $ret .= '=';
                    $ret .= "\015";
                    $ret .= "\012";
                    $lp = 1;
                }
                $ret .= $c;
                if($lp == 1 && $c == '.') {
                    $ret .= '.';
                    $lp++;
                }
            }
        }
    }

    return $ret;
}

?>