diff --git a/CHANGELOG b/CHANGELOG
index 9ca7fda9f..a6db41741 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,6 +1,7 @@
 CHANGELOG Roundcube Webmail
 ===========================
 
+- Support MathML in HTML message preview (#5182)
 - Rename Addressbook to Contacts (#5233)
 - Remove PHP mail() support, smtp_server is required now (#5340)
 - Display full message subject in onmouseover on truncated subject in mail view (#5346)
diff --git a/program/lib/Roundcube/rcube_washtml.php b/program/lib/Roundcube/rcube_washtml.php
index d03f04af4..e1058fd8d 100644
--- a/program/lib/Roundcube/rcube_washtml.php
+++ b/program/lib/Roundcube/rcube_washtml.php
@@ -76,7 +76,7 @@
  * - base URL support
  * - invalid HTML comments removal before parsing
  * - "fixing" unitless CSS values for XHTML output
- * - base url resolving
+ * - SVG and MathML support
  */
 
 /**
@@ -111,6 +111,15 @@ class rcube_washtml
         'feflood', 'fefunca', 'fefuncb', 'fefuncg', 'fefuncr', 'fegaussianblur',
         'feimage', 'femerge', 'femergenode', 'femorphology', 'feoffset',
         'fespecularlighting', 'fetile', 'feturbulence',
+        // MathML
+        'math', 'menclose', 'merror', 'mfenced', 'mfrac', 'mglyph', 'mi', 'mlabeledtr',
+        'mmuliscripts', 'mn', 'mo', 'mover', 'mpadded', 'mphantom', 'mroot', 'mrow',
+        'ms', 'mspace', 'msqrt', 'mstyle', 'msub', 'msup', 'msubsup', 'mtable', 'mtd',
+        'mtext', 'mtr', 'munder', 'munderover', 'maligngroup', 'malignmark',
+        'mprescripts', 'semantics', 'annotation', 'annotation-xml', 'none',
+        'infinity', 'matrix', 'matrixrow', 'ci', 'cn', 'sep', 'apply',
+        'plus', 'minus', 'eq', 'power', 'times', 'divide', 'csymbol', 'root',
+        'bvar', 'lowlimit', 'uplimit',
     );
 
     /* Ignore these HTML tags and their content */
@@ -153,11 +162,24 @@ class rcube_washtml
         'visibility', 'vert-adv-y', 'version', 'vert-origin-x', 'vert-origin-y', 'word-spacing',
         'wrap', 'writing-mode', 'xchannelselector', 'ychannelselector', 'x', 'x1', 'x2',
         'xmlns', 'y', 'y1', 'y2', 'z', 'zoomandpan',
+        // MathML
+        'accent', 'accentunder', 'bevelled', 'close', 'columnalign', 'columnlines',
+        'columnspan', 'denomalign', 'depth', 'display', 'displaystyle', 'encoding', 'fence',
+        'frame', 'largeop', 'length', 'linethickness', 'lspace', 'lquote',
+        'mathbackground', 'mathcolor', 'mathsize', 'mathvariant', 'maxsize',
+        'minsize', 'movablelimits', 'notation', 'numalign', 'open', 'rowalign',
+        'rowlines', 'rowspacing', 'rowspan', 'rspace', 'rquote', 'scriptlevel',
+        'scriptminsize', 'scriptsizemultiplier', 'selection', 'separator',
+        'separators', 'stretchy', 'subscriptshift', 'supscriptshift', 'symmetric', 'voffset',
+        'fontsize', 'fontweight', 'fontstyle', 'fontfamily', 'groupalign', 'edge', 'side',
     );
 
     /* Elements which could be empty and be returned in short form (<tag />) */
     static $void_elements = array('area', 'base', 'br', 'col', 'command', 'embed', 'hr',
         'img', 'input', 'keygen', 'link', 'meta', 'param', 'source', 'track', 'wbr',
+        // MathML
+        'sep', 'infinity', 'in', 'plus', 'eq', 'power', 'times', 'divide', 'root',
+        'maligngroup', 'none', 'mprescripts',
     );
 
     /* State for linked objects in HTML */
diff --git a/tests/Framework/Washtml.php b/tests/Framework/Washtml.php
index ef4b2e9a0..18dfcab54 100644
--- a/tests/Framework/Washtml.php
+++ b/tests/Framework/Washtml.php
@@ -239,7 +239,7 @@ class Framework_Washtml extends PHPUnit_Framework_TestCase
     /**
      * Test SVG cleanup
      */
-    function test_style_wash_svg()
+    function test_wash_svg()
     {
         $svg = '<?xml version="1.0" standalone="no"?>
 <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
@@ -274,4 +274,48 @@ class Framework_Washtml extends PHPUnit_Framework_TestCase
 
         $this->assertSame($washed, $exp, "SVG content");
     }
+
+    /**
+     * Test MathML cleanup
+     */
+    function test_wash_mathml()
+    {
+        $mathml = '<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body>
+            <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics>
+                <mrow>
+                    <msub><mi>I</mi><mi>D</mi></msub>
+                    <mo>=</mo>
+                    <mfrac><mn>1</mn><mn>2</mn></mfrac>
+                    <msub><mi>k</mi><mi>n</mi></msub>
+                    <mfrac><mi>W</mi><mi>L</mi></mfrac>
+                    <mo stretchy="false">(</mo>
+                    <msub><mi>V</mi><mrow><mi>G</mi><mi>S</mi></mrow></msub>
+                    <mo>-</mo><msub><mi>V</mi><mi>t</mi></msub><msup>
+                    <mo stretchy="false">)</mo><mn>2</mn></msup>
+                </mrow>
+                <annotation encoding="TeX">I_D = \frac{1}{2} k_n \frac{W}{L} (V_{GS}-V_t)^2</annotation>
+            </semantics></math>
+            </body></html>';
+
+        $exp = '<!-- html ignored --><!-- head ignored --><!-- meta ignored --><!-- body ignored -->
+            <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics>
+                <mrow>
+                    <msub><mi>I</mi><mi>D</mi></msub>
+                    <mo>=</mo>
+                    <mfrac><mn>1</mn><mn>2</mn></mfrac>
+                    <msub><mi>k</mi><mi>n</mi></msub>
+                    <mfrac><mi>W</mi><mi>L</mi></mfrac>
+                    <mo stretchy="false">(</mo>
+                    <msub><mi>V</mi><mrow><mi>G</mi><mi>S</mi></mrow></msub>
+                    <mo>-</mo><msub><mi>V</mi><mi>t</mi></msub><msup>
+                    <mo stretchy="false">)</mo><mn>2</mn></msup>
+                </mrow>
+                <annotation encoding="TeX">I_D = \frac{1}{2} k_n \frac{W}{L} (V_{GS}-V_t)^2</annotation>
+            </semantics></math>';
+
+        $washer = new rcube_washtml;
+        $washed = $washer->wash($mathml);
+
+        $this->assertSame(trim($washed), trim($exp), "MathML content");
+    }
 }