diff --git a/flake.nix b/flake.nix
index 64aa7c4..3139890 100644
--- a/flake.nix
+++ b/flake.nix
@@ -131,6 +131,21 @@
                       default = "emacsclient";
                       description = "Path to the emacsclient binary";
                     };
+                    debt_query = lib.mkOption {
+                      type = lib.types.str;
+                      default = "tag:unread and date:..1w";
+                      description = "notmuch query whose count drives the mail-debt severity color on the bar widget";
+                    };
+                    debt_warn_at = lib.mkOption {
+                      type = lib.types.int;
+                      default = 1;
+                      description = "Debt count at which the widget switches to the warn (orange) color";
+                    };
+                    debt_alarm_at = lib.mkOption {
+                      type = lib.types.int;
+                      default = 6;
+                      description = "Debt count at which the widget switches to the alarm (red) color";
+                    };
                   };
                   screenrec = {
                     enable = lib.mkOption {
@@ -210,6 +225,9 @@
                   enable = true;
                   notmuch_path = "notmuch";
                   emacsclient_command = "emacsclient";
+                  debt_query = "tag:unread and date:..1w";
+                  debt_warn_at = 1;
+                  debt_alarm_at = 6;
                 };
                 screenrec = {
                   enable = false;
diff --git a/sims/main.py b/sims/main.py
index 5c1e72d..5623372 100644
--- a/sims/main.py
+++ b/sims/main.py
@@ -131,7 +131,7 @@ def open_screenshot_menu():
 @Application.action()
 def refresh_notmuch():
     if notmuch_widget is not None:
-        notmuch_widget.service.update_unread_count()
+        notmuch_widget.service.update_counts()
 
 
 @Application.action()
diff --git a/sims/modules/notmuch.py b/sims/modules/notmuch.py
index 992be54..a518388 100644
--- a/sims/modules/notmuch.py
+++ b/sims/modules/notmuch.py
@@ -12,27 +12,33 @@ from loguru import logger
 from sims.config import NOTMUCH
 
 
+DEFAULT_DEBT_QUERY = "tag:unread and date:..1w"
+DEFAULT_DEBT_WARN_AT = 1
+DEFAULT_DEBT_ALARM_AT = 6
+
+
 class NotmuchService:
     def __init__(self, update_interval=60000):  # 1 minute default
         self.unread_count = 0
+        self.debt_count = 0
         self.callbacks = []
         self._update_interval = update_interval
         self._timer_id = None
 
         # Initial load
-        self.update_unread_count()
+        self.update_counts()
         # Start periodic updates
         self.start_monitoring()
 
     def connect(self, signal_name, callback):
         """Simple callback system to replace signals"""
-        if signal_name == "unread-changed":
+        if signal_name == "counts-changed":
             self.callbacks.append(callback)
 
-    def emit_unread_changed(self, count):
-        """Emit unread changed to all callbacks"""
+    def emit_counts_changed(self):
+        """Emit counts changed to all callbacks"""
         for callback in self.callbacks:
-            callback(self, count)
+            callback(self, self.unread_count, self.debt_count)
 
     def start_monitoring(self):
         """Start periodic unread count updates"""
@@ -57,21 +63,38 @@ class NotmuchService:
 
     def _periodic_update(self):
         """Periodic update callback"""
-        logger.info("[Notmuch] Performing periodic unread count update")
-        self.update_unread_count()
+        logger.info("[Notmuch] Performing periodic count update")
+        self.update_counts()
         return True  # Keep the timer running
 
     def get_cached_count(self):
         """Get cached unread count without triggering update"""
         return self.unread_count
 
-    def update_unread_count(self):
-        """Fetch unread email count from notmuch"""
+    def get_cached_debt_count(self):
+        """Get cached debt count without triggering update"""
+        return self.debt_count
+
+    def _run_count(self, notmuch_path, query):
+        cmd = [notmuch_path, "count", query]
+        logger.info(f"[Notmuch] Running command: {' '.join(cmd)}")
+        result = subprocess.run(
+            cmd,
+            capture_output=True,
+            text=True,
+            check=True,
+        )
+        out = result.stdout.strip()
+        return int(out) if out else 0
+
+    def update_counts(self):
+        """Fetch unread + debt counts from notmuch"""
         # Check if notmuch is enabled
         if not NOTMUCH.get("enable", True):
             logger.info("[Notmuch] Notmuch is disabled in config")
             self.unread_count = 0
-            self.emit_unread_changed(self.unread_count)
+            self.debt_count = 0
+            self.emit_counts_changed()
             return
 
         # Get notmuch path from config
@@ -81,42 +104,34 @@ class NotmuchService:
         if not shutil.which(notmuch_path):
             logger.warning(f"[Notmuch] notmuch not found at '{notmuch_path}'. Please install notmuch or configure the correct path.")
             self.unread_count = 0
-            self.emit_unread_changed(self.unread_count)
+            self.debt_count = 0
+            self.emit_counts_changed()
             return
 
+        debt_query = NOTMUCH.get("debt_query", DEFAULT_DEBT_QUERY)
+
         try:
-            # Get unread email count
-            cmd = [notmuch_path, "count", "tag:unread"]
-            logger.info(f"[Notmuch] Running command: {' '.join(cmd)}")
-            result = subprocess.run(
-                cmd,
-                capture_output=True,
-                text=True,
-                check=True,
+            self.unread_count = self._run_count(notmuch_path, "tag:unread")
+            self.debt_count = self._run_count(notmuch_path, debt_query)
+            logger.info(
+                f"[Notmuch] {self.unread_count} unread, {self.debt_count} aging (debt query: {debt_query!r})"
             )
-            logger.info(f"[Notmuch] Command stdout: '{result.stdout.strip()}'")
-            logger.info(f"[Notmuch] Command stderr: '{result.stderr.strip()}'")
-
-            if result.stdout.strip():
-                self.unread_count = int(result.stdout.strip())
-                logger.info(f"[Notmuch] Found {self.unread_count} unread emails")
-                self.emit_unread_changed(self.unread_count)
-            else:
-                self.unread_count = 0
-                self.emit_unread_changed(self.unread_count)
-
+            self.emit_counts_changed()
         except subprocess.CalledProcessError as e:
-            logger.error(f"[Notmuch] Failed to fetch unread count: {e}")
+            logger.error(f"[Notmuch] Failed to fetch counts: {e}")
             self.unread_count = 0
-            self.emit_unread_changed(self.unread_count)
+            self.debt_count = 0
+            self.emit_counts_changed()
         except ValueError as e:
-            logger.error(f"[Notmuch] Error parsing unread count: {e}")
+            logger.error(f"[Notmuch] Error parsing count: {e}")
             self.unread_count = 0
-            self.emit_unread_changed(self.unread_count)
+            self.debt_count = 0
+            self.emit_counts_changed()
         except Exception as e:
-            logger.error(f"[Notmuch] Error getting unread count: {e}")
+            logger.error(f"[Notmuch] Error getting counts: {e}")
             self.unread_count = 0
-            self.emit_unread_changed(self.unread_count)
+            self.debt_count = 0
+            self.emit_counts_changed()
 
 
 class NotmuchWidget(Button):
@@ -141,12 +156,14 @@ class NotmuchWidget(Button):
 
         # Initialize the service
         self.service = NotmuchService()
-        self.service.connect("unread-changed", self.update_display)
+        self.service.connect("counts-changed", self.update_display)
 
         logger.info("[Notmuch] Notmuch widget initialized")
 
         # Initial update
-        self.update_display(self.service, self.service.unread_count)
+        self.update_display(
+            self.service, self.service.unread_count, self.service.debt_count
+        )
 
     def open_email_client(self, button=None):
         """Open notmuch in emacsclient"""
@@ -161,18 +178,31 @@ class NotmuchWidget(Button):
         except Exception as e:
             logger.error(f"[Notmuch] Failed to open notmuch in emacsclient '{emacsclient_command}': {e}")
 
-    def update_display(self, service, count):
-        """Update the widget display with unread count"""
-        # Only show count if there are unread emails
-        if count > 0:
-            self.label.set_text(str(count))
+    def update_display(self, service, unread, debt):
+        """Update the widget display with unread + debt counts"""
+        warn_at = NOTMUCH.get("debt_warn_at", DEFAULT_DEBT_WARN_AT)
+        alarm_at = NOTMUCH.get("debt_alarm_at", DEFAULT_DEBT_ALARM_AT)
+
+        classes = ["notmuch-widget"]
+        if unread > 0:
+            self.label.set_text(str(unread))
             self.label.set_visible(True)
             self.icon.set_property("icon-name", "mail-unread-symbolic")
-            self.set_style_classes(["notmuch-widget", "has-unread"])
+            classes.append("has-unread")
         else:
             self.label.set_text("")
             self.label.set_visible(False)
             self.icon.set_property("icon-name", "mail-read-symbolic")
-            self.set_style_classes(["notmuch-widget", "no-unread"])
+            classes.append("no-unread")
 
-        logger.info(f"[Notmuch] Updated display: {count} unread emails")
\ No newline at end of file
+        if debt >= alarm_at:
+            classes.append("debt-alarm")
+        elif debt >= warn_at:
+            classes.append("debt-warn")
+
+        self.set_style_classes(classes)
+        self.set_tooltip_text(f"{unread} unread · {debt} aging")
+
+        logger.info(
+            f"[Notmuch] Updated display: {unread} unread, {debt} aging — classes={classes}"
+        )
\ No newline at end of file
diff --git a/sims/styles/notmuch.css b/sims/styles/notmuch.css
index a4ce92b..8a7d0b9 100644
--- a/sims/styles/notmuch.css
+++ b/sims/styles/notmuch.css
@@ -23,6 +23,22 @@
     background-color: var(--module-bg);
 }
 
+#notmuch-widget.debt-warn {
+    background-color: var(--orange);
+}
+
+#notmuch-widget.debt-warn:hover {
+    background-color: var(--gold);
+}
+
+#notmuch-widget.debt-alarm {
+    background-color: var(--red);
+}
+
+#notmuch-widget.debt-alarm:hover {
+    background-color: var(--pink);
+}
+
 #unread-count {
     color: var(--foreground);
     font-size: 14px;
@@ -30,6 +46,8 @@
     min-width: 16px;
 }
 
-#notmuch-widget.has-unread #unread-count {
+#notmuch-widget.has-unread #unread-count,
+#notmuch-widget.debt-warn #unread-count,
+#notmuch-widget.debt-alarm #unread-count {
     color: var(--background);
 }
\ No newline at end of file