Improve email contents (#1510)

Improve email contents

src/pretix/base/services/mail.py

@@ -14,7 +14,10 @@ import requests
 from bs4 import BeautifulSoup
 from celery import chain
 from django.conf import settings
-from django.core.mail import EmailMultiAlternatives, get_connection
+from django.core.mail import (
+    EmailMultiAlternatives, SafeMIMEMultipart, get_connection,
+)
+from django.core.mail.message import SafeMIMEText
 from django.template.loader import get_template
 from django.utils.translation import pgettext, ugettext as _
 from django_scopes import scope, scopes_disabled
@@ -232,16 +235,32 @@ def mail(email: str, subject: str, template: Union[str, LazyI18nString],
         chain(*task_chain).apply_async()
 
 
+class CustomEmail(EmailMultiAlternatives):
+    def _create_mime_attachment(self, content, mimetype):
+        """
+        Convert the content, mimetype pair into a MIME attachment object.
+
+        If the mimetype is message/rfc822, content may be an
+        email.Message or EmailMessage object, as well as a str.
+        """
+        basetype, subtype = mimetype.split('/', 1)
+        if basetype == 'multipart' and isinstance(content, SafeMIMEMultipart):
+            return content
+        return super()._create_mime_attachment(content, mimetype)
+
+
 @app.task(base=TransactionAwareTask, bind=True)
 def mail_send_task(self, *args, to: List[str], subject: str, body: str, html: str, sender: str,
                    event: int=None, position: int=None, headers: dict=None, bcc: List[str]=None,
                    invoices: List[int]=None, order: int=None, attach_tickets=False, user=None,
                    attach_ical=False) -> bool:
-    email = EmailMultiAlternatives(subject, body, sender, to=to, bcc=bcc, headers=headers)
+    email = CustomEmail(subject, body, sender, to=to, bcc=bcc, headers=headers)
     if html is not None:
+        html_message = SafeMIMEMultipart(_subtype='related', encoding=settings.DEFAULT_CHARSET)
         html_with_cid, cid_images = replace_images_with_cid_paths(html)
-        email = attach_cid_images(email, cid_images, verify_ssl=True)
-        email.attach_alternative(html_with_cid, "text/html")
+        html_message.attach(SafeMIMEText(html_with_cid, 'html', settings.DEFAULT_CHARSET))
+        attach_cid_images(html_message, cid_images, verify_ssl=True)
+        email.attach_alternative(html_message, "multipart/related")
 
     if user:
         user = User.objects.get(pk=user)
@@ -409,8 +428,6 @@ def attach_cid_images(msg, cid_images, verify_ssl=True):
             except:
                 logger.exception("ERROR attaching CID image %s[%s]" % (cid, image))
 
-    return msg
-
 
 def encoder_linelength(msg):
     """

src/pretix/base/templates/pretixbase/email/base.html

@@ -158,7 +158,7 @@
     <table class="layout" width="600" border="0" cellspacing="0">
         <!--[if !mso]><!-- -->
         <tr>
-            <td>
+            <td style="line-height: 0">
                 <img class="wide" src="data:image/png;base64,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"
                 style="max-height: 60px;">
             </td>
@@ -188,7 +188,7 @@
         {% endblock %}
         <!--[if !mso]><!-- -->
         <tr>
-            <td>
+            <td style="line-height: 0">
                 <br>
                 <img class="wide" src="data:image/png;base64,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"
                 style="max-height: 60px;">

src/pretix/base/templates/pretixbase/email/separator.html

@@ -1,8 +1,10 @@
 <!--[if !mso]><!-- -->
 <tr>
     <td>
-        <img class="wide" src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAlgAAAAoBAMAAADQ9ZkHAAAAA3NCSVQICAjb4U/gAAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAGXRFWHRTb2Z0d2FyZQB3d3cuaW5rc2NhcGUub3Jnm+48GgAAAC1QTFRF7u7u7+/v8PDw8fHx8vLy9PT09fX19/f3+Pj4+fn5+vr6/Pz8/f39/v7+////BLnnfgAAAKJJREFUaN7t1cGtgUEARtFfQkREDypQihpUoIQXpahADUqRiIgINdjehcXbSTjf8s5mchYzw9P+vQEBLFiwYMGChQAWLFiwYMFCAAsWLFhfipX9pe/S1+nH9EX6OX2Wfk2fpN/TR73QMgeH9E36Nn2fvko/pc/TL+nT9Fv6OP0xvB8sWLA+g+XZ9hvCggULFiwEsGDBggULFgJYsGDBgvXzewGTOlWA3NB0eQAAAABJRU5ErkJggg=="
-            style="max-height: 40px;">
+        <div style="line-height: 18px">&nbsp;</div>
+        <img class="wide" src="data:image/png;base64,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"
+            style="max-height: 4px;">
+        <div style="line-height: 18px">&nbsp;</div>
     </td>
 </tr>
 <!--<![endif]-->