diff --git a/modoboa/lib/email_utils.py b/modoboa/lib/email_utils.py
index 793304d8b..b216336bc 100644
--- a/modoboa/lib/email_utils.py
+++ b/modoboa/lib/email_utils.py
@@ -9,11 +9,11 @@ from email.utils import formataddr, formatdate, getaddresses, make_msgid
 import chardet
 import lxml.html
 from lxml.html import defs
-from lxml.html.clean import Cleaner
+from lxml_html_clean import Cleaner
 
 from django.core.mail import EmailMessage
 from django.template.loader import render_to_string
-from django.utils.encoding import smart_str, smart_str
+from django.utils.encoding import smart_str
 from django.utils.html import conditional_escape, escape
 from django.utils.translation import gettext as _
 
@@ -26,7 +26,7 @@ _RE_REMOVE_EXTRA_WHITESPACE = re.compile(r"\n\s*\n")
 _RE_CID = re.compile(r".*[ ]*cid=\"([^\"]*)\".*", re.I)
 
 
-class EmailAddress(object):
+class EmailAddress:
 
     def __init__(self, address):
         self.name, self.address = u2u_decode.decode_address(address)
@@ -39,7 +39,7 @@ class EmailAddress(object):
         return self.fulladdress
 
 
-class Email(object):
+class Email:
 
     _basic_headers = (
         "From",
diff --git a/modoboa/lib/tests/sample_messages/multipart-input.txt b/modoboa/lib/tests/sample_messages/multipart-input.txt
index ee0b51430..9b29082fd 100644
--- a/modoboa/lib/tests/sample_messages/multipart-input.txt
+++ b/modoboa/lib/tests/sample_messages/multipart-input.txt
@@ -57,7 +57,7 @@ This is an *html* /test /_message._
 :-)
 
 
--- 
+--
 Someone
 someone@example.net
 
@@ -83,12 +83,11 @@ Content-Transfer-Encoding: 7bit
     <img moz-do-not-send="false"
       src="cid:part1.D56823CE.7959DBD4@example.net" alt="" height="10"
       width="10"><br>
-    <pre class="moz-signature" cols="72">-- 
+    <pre class="moz-signature" cols="72">--
 someone
 <a class="moz-txt-link-abbreviated" href="mailto:someone@example.net">someone@example.net</a></pre>
   </body>
 </html>
-
 --------------D585B241EEF60F0F44EC20E5
 Content-Type: image/png;
  name="image.png"
diff --git a/modoboa/lib/tests/sample_messages/multipart-output-html_links.txt b/modoboa/lib/tests/sample_messages/multipart-output-html_links.txt
index 92c507ec5..67177a723 100644
--- a/modoboa/lib/tests/sample_messages/multipart-output-html_links.txt
+++ b/modoboa/lib/tests/sample_messages/multipart-output-html_links.txt
@@ -8,13 +8,8 @@
     <span class="moz-smiley-s1"><span>:-)</span></span><br>
     <br>
     <img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAIAAAACUFjqAAAACXBIWXMAAAsTAAALEwEAmpwYAAAAF0lEQVQY02NgYGD4//8/ThKfHASMRN0AfaqVa6MQxIQAAAAASUVORK5CYII=" alt="" height="10" width="10" target="_blank"><br>
-    <pre class="moz-signature" cols="72">-- 
+    <pre class="moz-signature" cols="72">--
 someone
 <a class="moz-txt-link-abbreviated" href="mailto:someone@example.net" target="_blank" rel="nofollow">someone@example.net</a></pre>
   </body>
-<span><b>Some <i>HTML</i> text</b>, a <a href="http://example.net" target="_blank" rel="nofollow">link</a>, an

-embedded image and an external image.<br>

-<img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAIAAAACUFjqAAAACXBIWXMAAAsTAAALEwEAmpwYAAAAF0lEQVQY02NgYGD4//8/ThKfHASMRN0AfaqVa6MQxIQAAAAASUVORK5CYII=" target="_blank"><br>

-<img src="http://example.net/image.png" target="_blank"><br>

-Nifty!</span>
-</div>
\ No newline at end of file
+</div>
diff --git a/modoboa/lib/tests/sample_messages/multipart-output-html_nolinks.txt b/modoboa/lib/tests/sample_messages/multipart-output-html_nolinks.txt
index 56d847fb8..00328ac8d 100644
--- a/modoboa/lib/tests/sample_messages/multipart-output-html_nolinks.txt
+++ b/modoboa/lib/tests/sample_messages/multipart-output-html_nolinks.txt
@@ -8,13 +8,8 @@
     <span class="moz-smiley-s1"><span>:-)</span></span><br>
     <br>
     <img alt="" height="10" width="10"><br>
-    <pre class="moz-signature" cols="72">-- 
+    <pre class="moz-signature" cols="72">--
 someone
 <a class="moz-txt-link-abbreviated">someone@example.net</a></pre>
   </body>
-<span><b>Some <i>HTML</i> text</b>, a <a target="_blank" rel="nofollow">link</a>, an

-embedded image and an external image.<br>

-<img target="_blank"><br>

-<img target="_blank"><br>

-Nifty!</span>
-</div>
\ No newline at end of file
+</div>
diff --git a/modoboa/lib/tests/sample_messages/multipart-output-plain_nolinks.txt b/modoboa/lib/tests/sample_messages/multipart-output-plain_nolinks.txt
index 8795edadc..855fa5ca7 100644
--- a/modoboa/lib/tests/sample_messages/multipart-output-plain_nolinks.txt
+++ b/modoboa/lib/tests/sample_messages/multipart-output-plain_nolinks.txt
@@ -2,6 +2,6 @@
 
 :-)
 
--- 
+--
 Someone
-someone@example.net</pre>
\ No newline at end of file
+someone@example.net</pre>
diff --git a/modoboa/lib/tests/test_email_utils.py b/modoboa/lib/tests/test_email_utils.py
index 963ed319a..1c6844ccc 100644
--- a/modoboa/lib/tests/test_email_utils.py
+++ b/modoboa/lib/tests/test_email_utils.py
@@ -34,10 +34,10 @@ class EmailTests(SimpleTestCase):
     output: {message_id}-output-{dformat}_{no,}links.txt
     """
 
-    def _get_expected_output(self, message_id, **kwargs):
+    def _get_expected_output(self, message_id: str, **kwargs) -> str:
         ext = kwargs["dformat"] if "dformat" in kwargs else "plain"
         ext += "_links" if "links" in kwargs and kwargs["links"] else "_nolinks"
-        message_path = os.path.join(SAMPLES_DIR, "%s-output-%s.txt" % (message_id, ext))
+        message_path = os.path.join(SAMPLES_DIR, f"{message_id}-output-{ext}.txt")
         assert os.path.isfile(message_path), "%s does not exist." % message_path
 
         with open(message_path, "rb") as fp:
@@ -46,11 +46,11 @@ class EmailTests(SimpleTestCase):
 
         return mail_text
 
-    def _test_email(self, message_id, **kwargs):
+    def _test_email(self, message_id: str, **kwargs) -> None:
         """Boiler plate code for testing e-mails."""
         expected_output = self._get_expected_output(message_id, **kwargs)
         output = EmailTestImplementation(message_id, **kwargs).body
-        self.assertEqual(output, expected_output)
+        self.assertEqual(output.strip("\n"), expected_output.strip("\n"))
 
     def test_invalid_links_value(self):
         """modoboa-amavis set links = "0"; in python "0" == True, fixed in PR 79
diff --git a/requirements.txt b/requirements.txt
index 4ff57358a..c314b0d8c 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -30,7 +30,7 @@ python-dateutil
 cryptography
 pytz
 requests
-lxml
+lxml[html_clean]
 chardet
 ovh
 oath