diff --git a/app/app/email/headers.py b/app/app/email/headers.py
index 788693b..bfbcb9a 100644
--- a/app/app/email/headers.py
+++ b/app/app/email/headers.py
@@ -21,6 +21,7 @@ LIST_UNSUBSCRIBE = "List-Unsubscribe"
 LIST_UNSUBSCRIBE_POST = "List-Unsubscribe-Post"
 RETURN_PATH = "Return-Path"
 AUTHENTICATION_RESULTS = "Authentication-Results"
+SL_QUEUE_ID = "X-SL-Queue-Id"
 
 # headers used to DKIM sign in order of preference
 DKIM_HEADERS = [
diff --git a/app/app/handler/dmarc.py b/app/app/handler/dmarc.py
index fc1a2d1..895fa70 100644
--- a/app/app/handler/dmarc.py
+++ b/app/app/handler/dmarc.py
@@ -30,7 +30,9 @@ def apply_dmarc_policy_for_forward_phase(
 ) -> Tuple[Message, Optional[str]]:
     spam_result = SpamdResult.extract_from_headers(msg, Phase.forward)
     if not DMARC_CHECK_ENABLED or not spam_result:
+        LOG.i("DMARC check disabled")
         return msg, None
+    LOG.i(f"Spam check result in {spam_result}")
 
     from_header = get_header_unicode(msg[headers.FROM])
 
@@ -150,8 +152,10 @@ def apply_dmarc_policy_for_reply_phase(
 ) -> Optional[str]:
     spam_result = SpamdResult.extract_from_headers(msg, Phase.reply)
     if not DMARC_CHECK_ENABLED or not spam_result:
+        LOG.i("DMARC check disabled")
         return None
 
+    LOG.i(f"Spam check result is {spam_result}")
     if spam_result.dmarc not in (
         DmarcCheckResult.quarantine,
         DmarcCheckResult.reject,
diff --git a/app/app/import_utils.py b/app/app/import_utils.py
index 9d4460e..6cb30cc 100644
--- a/app/app/import_utils.py
+++ b/app/app/import_utils.py
@@ -30,7 +30,10 @@ def handle_batch_import(batch_import: BatchImport):
 
     LOG.d("Download file %s from %s", batch_import.file, file_url)
     r = requests.get(file_url)
-    lines = [line.decode("utf-8") for line in r.iter_lines()]
+    # Replace invisible character
+    lines = [
+        line.decode("utf-8").replace("\ufeff", "").strip() for line in r.iter_lines()
+    ]
 
     import_from_csv(batch_import, user, lines)
 
diff --git a/app/email_handler.py b/app/email_handler.py
index aa2b06b..e77fcbb 100644
--- a/app/email_handler.py
+++ b/app/email_handler.py
@@ -875,6 +875,7 @@ def forward_email_to_mailbox(
         # References and In-Reply-To are used for keeping the email thread
         headers.REFERENCES,
         headers.IN_REPLY_TO,
+        headers.SL_QUEUE_ID,
         headers.LIST_UNSUBSCRIBE,
         headers.LIST_UNSUBSCRIBE_POST,
     ] + headers.MIME_HEADERS
diff --git a/app/tests/test_email_handler.py b/app/tests/test_email_handler.py
index 121c226..5b33c71 100644
--- a/app/tests/test_email_handler.py
+++ b/app/tests/test_email_handler.py
@@ -384,3 +384,30 @@ def test_break_loop_alias_as_mailbox(flask_client):
     msg[headers.SUBJECT] = random_string()
     result = email_handler.handle(envelope, msg)
     assert result == status.E525
+
+
+@mail_sender.store_emails_test_decorator
+def test_preserve_headers(flask_client):
+    headers_to_keep = [
+        headers.SUBJECT,
+        headers.DATE,
+        headers.MESSAGE_ID,
+        headers.REFERENCES,
+        headers.IN_REPLY_TO,
+        headers.SL_QUEUE_ID,
+    ] + headers.MIME_HEADERS
+    user = create_new_user()
+    alias = Alias.create_new_random(user)
+    envelope = Envelope()
+    envelope.mail_from = "somewhere@lo.cal"
+    envelope.rcpt_tos = [alias.email]
+    msg = EmailMessage()
+    for header in headers_to_keep:
+        msg[header] = header + "keep"
+    result = email_handler.handle(envelope, msg)
+    assert result == status.E200
+    sent_mails = mail_sender.get_stored_emails()
+    assert len(sent_mails) == 1
+    msg = sent_mails[0].msg
+    for header in headers_to_keep:
+        assert msg[header] == header + "keep"