diff --git a/email_forwarder.service b/email_forwarder.service
index ef609dd..cdf2ee2 100644
--- a/email_forwarder.service
+++ b/email_forwarder.service
@@ -3,6 +3,7 @@ Description=Email Forwarder
 OnFailure=email_forwarder-fail-notify.service
 
 [Service]
+Type=oneshot
 WorkingDirectory=${PROJECT_DIR}
 ExecStart=${PROJECT_DIR}/venv/bin/python -m email_forwarder
 EnvironmentFile=${PROJECT_DIR}/.env
diff --git a/email_forwarder/email_forwarder.py b/email_forwarder/email_forwarder.py
index 9191fdd..2c37654 100644
--- a/email_forwarder/email_forwarder.py
+++ b/email_forwarder/email_forwarder.py
@@ -197,6 +197,9 @@ class EmailForwarder:
             msg_id = msg.get("Message-ID")
             if not msg_id:
                 continue
+            # Collapse folded headers (embedded CRLF/whitespace) so the
+            # Message-ID is safe to embed in an IMAP SEARCH command.
+            msg_id = "".join(msg_id.split())
             if msg_id in self.processed_ids:
                 continue
             self.dest.ensure_folder_exists(folder)