diff --git a/static/js/emailLibrary.js b/static/js/emailLibrary.js
index 781e3a5..806d652 100644
--- a/static/js/emailLibrary.js
+++ b/static/js/emailLibrary.js
@@ -4640,6 +4640,7 @@ function _updateBulkBar() {
 async function _bulkAction(action) {
   const uids = Array.from(state._selectedUids);
   if (uids.length === 0) return;
+  let failedReadSync = 0;
   if (action === 'delete') {
     const ok = await styledConfirm(
       `Delete ${uids.length} selected email${uids.length === 1 ? '' : 's'}?`,
@@ -4655,11 +4656,19 @@ async function _bulkAction(action) {
       } else if (action === 'delete') {
         await fetch(`${API_BASE}/api/email/delete/${uid}?folder=${encodeURIComponent(state._libFolder)}${_acct()}`, { method: 'DELETE' });
       } else if (action === 'read' || action === 'unread') {
-        // Local toggle for now (no backend endpoint yet)
-        const em = state._libEmails.find(e => e.uid === uid);
-        if (em) em.is_read = (action === 'read');
+        const endpoint = action === 'read' ? 'mark-read' : 'mark-unread';
+        const res = await fetch(`${API_BASE}/api/email/${endpoint}/${uid}?folder=${encodeURIComponent(state._libFolder)}${_acct()}`, { method: 'POST' });
+        let data = null;
+        try { data = await res.json(); } catch (_) {}
+        if (!res.ok || data?.success === false) {
+          throw new Error(data?.error || `HTTP ${res.status}`);
+        }
+        _syncEmailReadState(uid, action === 'read');
       }
-    } catch (e) { console.error(`Failed to ${action} ${uid}:`, e); }
+    } catch (e) {
+      if (action === 'read' || action === 'unread') failedReadSync += 1;
+      console.error(`Failed to ${action} ${uid}:`, e);
+    }
   }
 
   if (action === 'archive' || action === 'delete') {
@@ -4671,8 +4680,10 @@ async function _bulkAction(action) {
   state._selectMode = false;
   _updateBulkBar();
   _renderGrid();
-  // Sync the local mutation (delete/archive, or in-place read/unread
-  // flag flips on email objects) into the SWR cache so reopen doesn't
+  if (failedReadSync > 0) {
+    showToast(`Failed to update ${failedReadSync} email${failedReadSync === 1 ? '' : 's'}`);
+  }
+  // Sync successful local mutations into the SWR cache so reopen doesn't
   // briefly show the pre-bulk state.
   _libCacheWriteBack();
 }
diff --git a/tests/test_email_library_bulk_actions.py b/tests/test_email_library_bulk_actions.py
new file mode 100644
index 0000000..900e0a6
--- /dev/null
+++ b/tests/test_email_library_bulk_actions.py
@@ -0,0 +1,36 @@
+from pathlib import Path
+
+
+_REPO = Path(__file__).resolve().parents[1]
+_EMAIL_LIBRARY = _REPO / "static" / "js" / "emailLibrary.js"
+
+
+def _bulk_action_source() -> str:
+    text = _EMAIL_LIBRARY.read_text(encoding="utf-8")
+    start = text.index("async function _bulkAction(action)")
+    end = text.index("\n}\n\n// _extractName", start) + 3
+    return text[start:end]
+
+
+def test_email_bulk_read_unread_calls_provider_write_routes():
+    """Bulk read/unread must persist to IMAP/provider, not only mutate UI state.
+
+    Regression for issue #800's email follow-up: list select -> Actions ->
+    Mark Read used to update `em.is_read` locally and cache that fake state,
+    then refresh from the provider made the message unread again.
+    """
+    src = _bulk_action_source()
+
+    assert "Local toggle for now" not in src
+    assert "mark-read" in src
+    assert "mark-unread" in src
+    assert "method: 'POST'" in src
+    assert "_syncEmailReadState(uid, action === 'read')" in src
+
+
+def test_email_bulk_read_unread_checks_backend_success_before_syncing_cache():
+    src = _bulk_action_source()
+
+    assert "data?.success === false" in src
+    assert "throw new Error(data?.error" in src
+    assert "_libCacheWriteBack()" in src