diff --git a/openerp/addons/base/tests/test_mail.py b/openerp/addons/base/tests/test_mail.py
index ec9877f895d..8186674b964 100644
--- a/openerp/addons/base/tests/test_mail.py
+++ b/openerp/addons/base/tests/test_mail.py
@@ -330,6 +330,13 @@ class TestCleaner(unittest.TestCase):
         for ext in test_mail_examples.BUG_3_OUT:
             self.assertNotIn(ext, new_html, 'html_email_cleaner did not removed invalid content')
 
+    def test_80_remove_classes(self):
+        new_html = html_email_clean(test_mail_examples.REMOVE_CLASS, remove=True)
+        for ext in test_mail_examples.REMOVE_CLASS_IN:
+            self.assertIn(ext, new_html, 'html_email_cleaner wrongly removed classes')
+        for ext in test_mail_examples.REMOVE_CLASS_OUT:
+            self.assertNotIn(ext, new_html, 'html_email_cleaner did not removed correctly unwanted classes')
+
     def test_90_misc(self):
         # False boolean for text must return empty string
         new_html = html_email_clean(False)
diff --git a/openerp/addons/base/tests/test_mail_examples.py b/openerp/addons/base/tests/test_mail_examples.py
index 97a34c45e55..3342876bf73 100644
--- a/openerp/addons/base/tests/test_mail_examples.py
+++ b/openerp/addons/base/tests/test_mail_examples.py
@@ -91,12 +91,12 @@ OERP_WEBSITE_HTML_1 = """
 
 OERP_WEBSITE_HTML_1_IN = [
     'Manage your company most important asset: People',
-    'img class="img-rounded img-responsive" src="/website/static/src/img/china_thumb.jpg"',
+    'src="/website/static/src/img/china_thumb.jpg"',
 ]
 OERP_WEBSITE_HTML_1_OUT = [
     'Break down information silos.',
     'Keep track of the vacation days accrued by each employee',
-    'img class="img-rounded img-responsive" src="/website/static/src/img/deers_thumb.jpg',
+    'src="/website/static/src/img/deers_thumb.jpg',
 ]
 
 OERP_WEBSITE_HTML_2 = """
@@ -205,7 +205,7 @@ OERP_WEBSITE_HTML_2_IN = [
 ]
 OERP_WEBSITE_HTML_2_OUT = [
     'Make every employee feel more connected',
-    'img class="img-responsive shadow" src="/website/static/src/img/text_image.png',
+    'src="/website/static/src/img/text_image.png',
 ]
 
 TEXT_1 = """I contact you about our meeting tomorrow. Here is the schedule I propose:
@@ -1173,3 +1173,34 @@ BUG_3_IN = [
 BUG_3_OUT = [
     'New kanban view of documents'
 ]
+
+REMOVE_CLASS = """
+<div style="FONT-SIZE: 12pt; FONT-FAMILY: 'Times New Roman'; COLOR: #000000">
+    <div>Hello</div>
+    <div>I have just installed Odoo 9 and I've got the following error:</div>
+    <div>&nbsp;</div>
+    <div class="openerp openerp_webclient_container oe_webclient">
+        <div class="oe_loading" style="DISPLAY: none">&nbsp;</div>
+    </div>
+    <div class="modal-backdrop in"></div>
+    <div role="dialog" tabindex="-1" aria-hidden="false" class="modal in" style="DISPLAY: block" data-backdrop="static">
+        <div class="modal-dialog modal-lg">
+            <div class="modal-content openerp">
+                <div class="modal-header"> 
+                    <h4 class="modal-title">Odoo Error<span class="o_subtitle text-muted"></span></h4>
+                </div>
+                <div class="o_error_detail modal-body">
+                    <pre>An error occured in a modal and I will send you back the html to try opening one on your end</pre>
+                </div>
+            </div>
+        </div>
+    </div>
+</div>
+"""
+
+REMOVE_CLASS_IN = [
+    'An error occured in a modal and I will send you back the html to try opening one on your end'
+]
+REMOVE_CLASS_OUT = [
+    '<div class="modal-backdrop in">'
+]
\ No newline at end of file
diff --git a/openerp/tools/mail.py b/openerp/tools/mail.py
index 5f82df93af9..2e44cfc7395 100644
--- a/openerp/tools/mail.py
+++ b/openerp/tools/mail.py
@@ -26,6 +26,7 @@ _logger = logging.getLogger(__name__)
 
 tags_to_kill = ["script", "head", "meta", "title", "link", "style", "frame", "iframe", "base", "object", "embed"]
 tags_to_remove = ['html', 'body']
+whitelist_classes = set(['WordSection1', 'MsoNormal', 'SkyDrivePlaceholder', 'oe_mail_expand', 'stopSpelling'])
 
 # allow new semantic HTML5 tags
 allowed_tags = clean.defs.tags | frozenset('article section header footer hgroup nav aside figure main'.split() + [etree.Comment])
@@ -292,6 +293,11 @@ def html_email_clean(html, remove=False, shorten=False, max_length=300, expand_o
 
     if expand_options is None:
         expand_options = {}
+    whitelist_classes_local = whitelist_classes.copy()
+    if expand_options.get('oe_expand_container_class'):
+        whitelist_classes_local.add(expand_options.get('oe_expand_container_class'))
+    if expand_options.get('oe_expand_a_class'):
+        whitelist_classes_local.add(expand_options.get('oe_expand_a_class'))
 
     if not html or not isinstance(html, basestring):
         return html
@@ -336,6 +342,7 @@ def html_email_clean(html, remove=False, shorten=False, max_length=300, expand_o
     quoted = False
     quote_begin = False
     overlength = False
+    replace_class = False
     overlength_section_id = None
     overlength_section_count = 0
     cur_char_nbr = 0
@@ -347,6 +354,17 @@ def html_email_clean(html, remove=False, shorten=False, max_length=300, expand_o
         # do not take into account multiple spaces that are displayed as max 1 space in html
         node_text = ' '.join((node.text and node.text.strip(' \t\r\n') or '').split())
 
+        # remove unwanted classes from node
+        if node.get('class'):
+            sanitize_classes = []
+            for _class in node.get('class').split(' '):
+                if _class in whitelist_classes_local:
+                    sanitize_classes.append(_class)
+                else:
+                    sanitize_classes.append('cleaned_'+_class)
+                    replace_class = True
+            node.set('class', ' '.join(sanitize_classes))
+
         # root: try to tag the client used to write the html
         if 'WordSection1' in node.get('class', '') or 'MsoNormal' in node.get('class', ''):
             root.set('msoffice', '1')
@@ -448,7 +466,7 @@ def html_email_clean(html, remove=False, shorten=False, max_length=300, expand_o
                 node_class = node.get('class', '') + ' oe_mail_cleaned'
                 node.set('class', node_class)
 
-    if not overlength and not quote_begin and not quoted:
+    if not overlength and not quote_begin and not quoted and not replace_class:
         return html
 
     # html: \n that were tail of elements have been encapsulated into <span> -> back to \n