diff --git a/.env b/.env
index c42ae89e92dda8fe1b7d18aaf347c8cae5079bea..3c54915509c70b99be51360273988f2a929324a7 100644
--- a/.env
+++ b/.env
@@ -34,6 +34,7 @@ CERN_OIDC_CLIENT_SECRET=fill-me
 #EMAIL_BACKEND=vendor.django_mail.backends.smimesmtp.EmailBackend
 #EMAIL_SMIME_CERT_FILE_PATH=/etc/notifications-noreply.pem
 #EMAIL_SMIME_CERT_KEY_FILE_PATH=/etc/notifications-noreply-key.pem
+#EMAIL_SMIME_CERT_INTERMEDIATE_FILE_PATH=/etc/notifications-noreply-intermediate.pem
 
 # Auditing
 ETCD_HOST=etcd
diff --git a/notifications-noreply-intermediate.pem b/notifications-noreply-intermediate.pem
new file mode 100644
index 0000000000000000000000000000000000000000..05ec33cb8d65393b9a1ed4cfdc0e0af74490ea36
--- /dev/null
+++ b/notifications-noreply-intermediate.pem
@@ -0,0 +1,35 @@
+-----BEGIN CERTIFICATE-----
+MIIGEDCCA/igAwIBAgIQTZQsENQ74JQJxYEtOisGTzANBgkqhkiG9w0BAQwFADCB
+iDELMAkGA1UEBhMCVVMxEzARBgNVBAgTCk5ldyBKZXJzZXkxFDASBgNVBAcTC0pl
+cnNleSBDaXR5MR4wHAYDVQQKExVUaGUgVVNFUlRSVVNUIE5ldHdvcmsxLjAsBgNV
+BAMTJVVTRVJUcnVzdCBSU0EgQ2VydGlmaWNhdGlvbiBBdXRob3JpdHkwHhcNMTgx
+MTAyMDAwMDAwWhcNMzAxMjMxMjM1OTU5WjCBljELMAkGA1UEBhMCR0IxGzAZBgNV
+BAgTEkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4GA1UEBxMHU2FsZm9yZDEYMBYGA1UE
+ChMPU2VjdGlnbyBMaW1pdGVkMT4wPAYDVQQDEzVTZWN0aWdvIFJTQSBDbGllbnQg
+QXV0aGVudGljYXRpb24gYW5kIFNlY3VyZSBFbWFpbCBDQTCCASIwDQYJKoZIhvcN
+AQEBBQADggEPADCCAQoCggEBAMo87ZQKQf/e+Ua56NY75tqSvysQTqoavIK9viYc
+KSoq0s2cUIE/bZQu85eoZ9X140qOTKl1HyLTJbazGl6nBEibivHbSuejQkq6uIgy
+miqvTcTlxZql19szfBxxo0Nm9l79L9S+TZNTEDygNfcXlkHKRhBhVFHdJDfqB6Mf
+i/Wlda43zYgo92yZOpCWjj2mz4tudN55/yE1+XvFnz5xsOFbme/SoY9WAa39uJOR
+HtbC0x7C7aYivToxuIkEQXaumf05Vcf4RgHs+Yd+mwSTManRy6XcCFJE6k/LHt3n
+dD3sA3If/JBz6OX2ZebtQdHnKav7Azf+bAhudg7PkFOTuRMCAwEAAaOCAWQwggFg
+MB8GA1UdIwQYMBaAFFN5v1qqK0rPVIDh2JvAnfKyA2bLMB0GA1UdDgQWBBQJwPL8
+C9qU21/+K9+omULPyeCtADAOBgNVHQ8BAf8EBAMCAYYwEgYDVR0TAQH/BAgwBgEB
+/wIBADAdBgNVHSUEFjAUBggrBgEFBQcDAgYIKwYBBQUHAwQwEQYDVR0gBAowCDAG
+BgRVHSAAMFAGA1UdHwRJMEcwRaBDoEGGP2h0dHA6Ly9jcmwudXNlcnRydXN0LmNv
+bS9VU0VSVHJ1c3RSU0FDZXJ0aWZpY2F0aW9uQXV0aG9yaXR5LmNybDB2BggrBgEF
+BQcBAQRqMGgwPwYIKwYBBQUHMAKGM2h0dHA6Ly9jcnQudXNlcnRydXN0LmNvbS9V
+U0VSVHJ1c3RSU0FBZGRUcnVzdENBLmNydDAlBggrBgEFBQcwAYYZaHR0cDovL29j
+c3AudXNlcnRydXN0LmNvbTANBgkqhkiG9w0BAQwFAAOCAgEAQUR1AKs5whX13o6V
+bTJxaIwA3RfXehwQOJDI47G9FzGR87bjgrShfsbMIYdhqpFuSUKzPM1ZVPgNlT+9
+istp5UQNRsJiD4KLu+E2f102qxxvM3TEoGg65FWM89YN5yFTvSB5PelcLGnCLwRf
+CX6iLPvGlh9j30lKzcT+mLO1NLGWMeK1w+vnKhav2VuQVHwpTf64ZNnXUF8p+5JJ
+pGtkUG/XfdJ5jR3YCq8H0OPZkNoVkDQ5CSSF8Co2AOlVEf32VBXglIrHQ3v9AAS0
+yPo4Xl1FdXqGFe5TcDQSqXh3TbjugGnG+d9yZX3lB8bwc/Tn2FlIl7tPbDAL4jNd
+UNA7jGee+tAnTtlZ6bFz+CsWmCIb6j6lDFqkXVsp+3KyLTZGXq6F2nnBtN4t5jO3
+ZIj2gpIKHAYNBAWLG2Q2fG7Bt2tPC8BLC9WIM90gbMhAmtMGquITn/2fORdsNmaV
+3z/sPKuIn8DvdEhmWVfh0fyYeqxGlTw0RfwhBlakdYYrkDmdWC+XszE19GUi8K8p
+lBNKcIvyg2omAdebrMIHiAHAOiczxX/aS5ABRVrNUDcjfvp4hYbDOO6qHcfzy/uY
+0fO5ssebmHQREJJA3PpSgdVnLernF6pthJrGkNDPeUI05svqw1o5A2HcNzLOpklh
+NwZ+4uWYLcAi14ACHuVvJsmzNic=
+-----END CERTIFICATE-----
diff --git a/notifications_consumer/config.py b/notifications_consumer/config.py
index 4b442959f9274e5407074bc950874be2a4d46e08..3edfa6c2ab2420f31aba2eeba16dea354acd553a 100644
--- a/notifications_consumer/config.py
+++ b/notifications_consumer/config.py
@@ -61,6 +61,7 @@ class Config:
 
     EMAIL_SMIME_CERT_FILE_PATH = os.getenv("EMAIL_SMIME_CERT_FILE_PATH")
     EMAIL_SMIME_CERT_KEY_FILE_PATH = os.getenv("EMAIL_SMIME_CERT_KEY_FILE_PATH")
+    EMAIL_SMIME_CERT_INTERMEDIATE_FILE_PATH = os.getenv("EMAIL_SMIME_CERT_INTERMEDIATE_FILE_PATH")
 
     NOREPLY_ADDRESS = os.getenv("NOREPLY_ADDRESS", "notifications-noreply@cern.ch")
 
diff --git a/vendor/django_mail/backends/smimesmtp.py b/vendor/django_mail/backends/smimesmtp.py
index 1689faf99f26b4c36d7462692db0fe5b90c37e44..ef94492e32ff1b72e61ff3afa0237919752e544d 100644
--- a/vendor/django_mail/backends/smimesmtp.py
+++ b/vendor/django_mail/backends/smimesmtp.py
@@ -158,7 +158,13 @@ class EmailBackend(BaseEmailBackend):
         to_sign = email_message.message()
         key_signer = Config.EMAIL_SMIME_CERT_KEY_FILE_PATH
         cert_signer = Config.EMAIL_SMIME_CERT_FILE_PATH
-        signed_message = sign_message(to_sign, key_signer, cert_signer, multipart_class=SafeMIMEMultipart)
+        cert_intermediate = Config.EMAIL_SMIME_CERT_INTERMEDIATE_FILE_PATH
+        signed_message = sign_message(
+            to_sign, 
+            key_signer, 
+            cert_signer, 
+            additional_certs=[cert_intermediate], 
+            multipart_class=SafeMIMEMultipart)
 
         try:
             self.connection.sendmail(