--- tests/Zend/MimeTest.php	(revision 23450)
+++ tests/Zend/MimeTest.php	(working copy)
@@ -68,19 +68,59 @@
         $this->assertTrue(Zend_Mime::isPrintable('Test without special chars'));
     }
 
-    public function testQP()
+    public function testQuotedPrintableEncoding()
     {
-        $text = "This is a cool Test Text with special chars: ����\n"
-              . "and with multiple lines���� some of the Lines are long, long"
-              . ", long, long, long, long, long, long, long, long, long, long"
-              . ", long, long, long, long, long, long, long, long, long, long"
-              . ", long, long, long, long, long, long, long, long, long, long"
-              . ", long, long, long, long and with ����";
+        $text = $this->_getQuotedPrintableStringSource();
+        $qp   = Zend_Mime::encodeQuotedPrintable($text);
+        $this->assertEquals(quoted_printable_decode($qp), $text);
+    }
 
-        $qp = Zend_Mime::encodeQuotedPrintable($text);
+    /**
+     * When PHP quoted-printable methods are available, Zend_Mime skips using
+     * its internal encoding methods.  So, this test directly tests
+     * Zend_Mime's internal encoding method.
+     */
+    public function testInternalQuotedPrintableEncoding()
+    {
+        if (!function_exists('quoted_printable_encode') && !function_exists('imap_8bit')) {
+            $this->markTestSkipped('no PHP quoted-printable encoding methods found');
+        }
+
+        $text = $this->_getQuotedPrintableStringSource();
+
+        $qp = QuotedPrintableTest::forceEncodeQuotedPrintableInternally($text);
         $this->assertEquals(quoted_printable_decode($qp), $text);
+
+        // ensure both internal and PHP encoding result in identical decoded result
+        $qpFromPhp  = Zend_Mime::encodeQuotedPrintable($text);
+        $this->assertSame(quoted_printable_decode($qp), quoted_printable_decode($qpFromPhp));
     }
 
+    public function testLineLengthIsConfigurableInQuotedPrintableEncoding()
+    {
+        $text = $this->_getQuotedPrintableStringSource();
+
+        $qp = Zend_Mime::encodeQuotedPrintable($text, 40);
+        foreach (explode(Zend_Mime::LINEEND, $qp) as $line) {
+            if(strlen($line) > 40) {
+                $this->fail("Line '".$line."' is ".strlen($line)." chars long, only 40 allowed.");
+            }
+        }
+    }
+    
+    public function testLineEndingsAreConfigurableInQuotedPrintableEncoding()
+    {
+        $text = $this->_getQuotedPrintableStringSource();
+
+        $qp = Zend_Mime::encodeQuotedPrintable($text, Zend_Mime::LINELENGTH, "\n");
+        $this->assertContains("=\n", $qp);
+        $this->assertNotContains("=\r\n", $qp);
+
+        $qp = Zend_Mime::encodeQuotedPrintable($text, Zend_Mime::LINELENGTH, "\r\n");
+        $this->assertNotContains("=\n", $qp);
+        $this->assertContains("=\r\n", $qp);
+    }
+
     public function testBase64()
     {
         $content = str_repeat("\x88\xAA\xAF\xBF\x29\x88\xAA\xAF\xBF\x29\x88\xAA\xAF", 4);
@@ -163,4 +203,26 @@
             }
         }
     }
+
+    protected function _getQuotedPrintableStringSource()
+    {
+        return "This is a cool Test Text with special chars: ����\n"
+              . "and with multiple lines���� some of the Lines are long, long"
+              . ", long, long, long, long, long, long, long, long, long, long"
+              . ", long, long, long, long, long, long, long, long, long, long"
+              . ", long, long, long, long, long, long, long, long, long, long"
+              . ", long, long, long, long and with ����";
+    }
 }
+
+/**
+ * Class for testing internal Zend_Mime quoted-printable encoding
+ */
+class QuotedPrintableTest extends Zend_Mime
+{
+    static public function forceEncodeQuotedPrintableInternally($str)
+    {
+        $str = self::_encodeQuotedPrintableInternal($str);
+        return self::_breakQuotedPrintableLines($str, self::LINELENGTH, self::LINEEND);
+    }
+}
\ No newline at end of file
Index: library/Zend/Mime.php
===================================================================
--- library/Zend/Mime.php	(revision 23450)
+++ library/Zend/Mime.php	(working copy)
@@ -126,14 +126,29 @@
         $lineLength = self::LINELENGTH,
         $lineEnd = self::LINEEND)
     {
-        $out = '';
         $str = self::_encodeQuotedPrintable($str);
+        $str = self::_breakQuotedPrintableLines($str, $lineLength, $lineEnd);
+        return $str;
+    }
 
-        // Split encoded text into separate lines
+    /**
+     * Split encoded quoted-printable text onto separate lines
+     *
+     * @param string $str
+     * @param integer $lineLength
+     * @param string $lineEnd
+     * @return string
+     */
+    protected static function _breakQuotedPrintableLines($str,
+            $lineLength = self::LINELENGTH,
+            $lineEnd = self::LINEEND)
+    {
+        $out = '';
         while ($str) {
             $ptr = strlen($str);
             if ($ptr > $lineLength) {
-                $ptr = $lineLength;
+                // limit to $lineLength - 1 to leave room for the soft '=' line break
+                $ptr = $lineLength - 1;
             }
 
             // Ensure we are not splitting across an encoded character
@@ -165,6 +180,39 @@
      */
     private static function _encodeQuotedPrintable($str)
     {
+        // PHP or extension functions are much faster, use if available
+        if (function_exists('quoted_printable_encode') ||
+            function_exists('imap_8bit')) {
+
+            if (function_exists('quoted_printable_encode')) {
+                $str = quoted_printable_encode($str);
+            } else {
+                $str = imap_8bit($str);
+            }
+
+            // consolidate on single line like internal encoding method.
+            // this allows later breaking on custom line lengths
+            $str = str_replace("=\r\n", '', $str);
+
+            // PHP methods skip encoding trailing whitespace,
+            // so trim it off because it wasn't encoded
+            $str = rtrim($str);
+
+            return $str;
+        } else {
+            return self::_encodeQuotedPrintableInternal($str);
+        }
+    }
+
+    /**
+     * Convert a string into quoted printable format using the internal (slow!)
+     * method.
+     *
+     * @param string $str
+     * @return string
+     */
+    protected static function _encodeQuotedPrintableInternal($str)
+    {
         $str = str_replace('=', '=3D', $str);
         $str = str_replace(self::$qpKeys, self::$qpReplaceValues, $str);
         $str = rtrim($str);
Index: documentation/manual/en/module_specs/Zend_Mime.xml
===================================================================
--- documentation/manual/en/module_specs/Zend_Mime.xml	(revision 23450)
+++ documentation/manual/en/module_specs/Zend_Mime.xml	(working copy)
@@ -187,6 +187,17 @@
             </itemizedlist>
         </para>
     </sect2>
+
+    <sect2 id="zend.mime.mime.performance">
+        <title>Performance</title>
+
+        <para>
+           Enabling the PHP <acronym>IMAP</acronym> extension on PHP versions
+           prior to PHP 5.3.0 will noticeably speed up
+           <methodname>Zend_Mime::encodeQuotedPrintable()</methodname>.  This
+           is not necessary on PHP 5.3.0+.
+        </para>
+    </sect2>
 </sect1>
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