Hotfix linkified placeholders (#5663)

* Fix linkify placeholders

* Add URL test

src/pretix/base/email.py

@@ -24,6 +24,7 @@ from itertools import groupby
 from smtplib import SMTPResponseException
 from typing import TypeVar
 
+import bleach
 import css_inline
 from django.conf import settings
 from django.core.mail.backends.smtp import EmailBackend
@@ -34,7 +35,10 @@ from django.utils.translation import get_language, gettext_lazy as _
 
 from pretix.base.models import Event
 from pretix.base.signals import register_html_mail_renderers
-from pretix.base.templatetags.rich_text import markdown_compile_email
+from pretix.base.templatetags.rich_text import (
+    DEFAULT_CALLBACKS, EMAIL_RE, URL_RE, abslink_callback,
+    markdown_compile_email, truelink_callback,
+)
 from pretix.helpers.format import SafeFormatter, format_map
 
 from pretix.base.services.placeholders import (  # noqa
@@ -139,7 +143,18 @@ class TemplateBasedMailRenderer(BaseHTMLMailRenderer):
     def render(self, plain_body: str, plain_signature: str, subject: str, order, position, context) -> str:
         body_md = self.compile_markdown(plain_body, context)
         if context:
-            body_md = format_map(body_md, context=context, mode=SafeFormatter.MODE_RICH_TO_HTML)
+            linker = bleach.Linker(
+                url_re=URL_RE,
+                email_re=EMAIL_RE,
+                callbacks=DEFAULT_CALLBACKS + [truelink_callback, abslink_callback],
+                parse_email=True
+            )
+            body_md = format_map(
+                body_md,
+                context=context,
+                mode=SafeFormatter.MODE_RICH_TO_HTML,
+                linkifier=linker
+            )
         htmlctx = {
             'site': settings.PRETIX_INSTANCE_NAME,
             'site_url': settings.SITE_URL,