update

seahub/utils/__init__.py

@@ -18,7 +18,6 @@ from urllib.parse import urlparse
 
 from constance import config
 import seaserv
-from django.core.mail.backends.smtp import EmailBackend
 from seaserv import seafile_api, ccnet_api
 
 from django.urls import reverse
@@ -40,7 +39,7 @@ from seahub.settings import MEDIA_URL, LOGO_PATH, \
 from seahub.constants import PERMISSION_READ_WRITE
 from seahub.utils.db_api import SeafileDB
 from seahub.onlyoffice.settings import ENABLE_ONLYOFFICE, ONLYOFFICE_FILE_EXTENSION
-from seahub.utils.mail import add_smime_sign
+
 
 try:
     from seahub.settings import EVENTS_CONFIG_FILE
@@ -1003,6 +1002,7 @@ def send_html_email(subject, con_template, con_context, from_email, to_email,
     """
 
     # get logo path
+    from seahub.utils.mail import add_smime_sign
     logo_path = LOGO_PATH
     custom_logo_file = os.path.join(MEDIA_ROOT, CUSTOM_LOGO_PATH)
     if os.path.exists(custom_logo_file):

seahub/utils/mail.py

@@ -1,7 +1,7 @@
 # Copyright (c) 2012-2016 Seafile Ltd.
 import os
 import logging
-from email.mime.text import MIMEText
+from email.mime.application import MIMEApplication
 from cryptography.hazmat.primitives import serialization, hashes
 from cryptography.hazmat.primitives.serialization import pkcs7
 from cryptography import x509
@@ -52,7 +52,7 @@ def add_smime_sign(msg):
     signature_b64 = base64.b64encode(pkcs7_signature).decode()
     
     # Create the S/MIME signature part
-    sig_part = MIMEText(
+    sig_part = MIMEApplication(
         signature_b64,
         "pkcs7-signature",
         _charset="utf-8"