diff --git a/components/admin/org/sections/delegates-section.tsx b/components/admin/org/sections/delegates-section.tsx
index 59b4993fd..1fecb99c5 100644
--- a/components/admin/org/sections/delegates-section.tsx
+++ b/components/admin/org/sections/delegates-section.tsx
@@ -6,11 +6,11 @@ import { RestrictionRow } from '../org-page';
 import type { OrgPolicyDraft } from '../use-org-policy-draft';
 
 const DELEGATION = RESTRICTION_KEYS.find((def) => def.key === 'delegation')!;
-const DELEGATION_RIGHTS = RESTRICTION_KEYS.find((def) => def.key === 'delegationRights')!;
+const SHARING_RIGHTS = RESTRICTION_KEYS.find((def) => def.key === 'sharingRights')!;
 
-/** Organisation > Sharing > Delegates: whether users may delegate, and which rights. */
+/** Organisation > Sharing > Delegates: whether users may delegate, and which rights any share dialog offers. */
 export function DelegatesSection({ draft }: { draft: OrgPolicyDraft }) {
-  const rights = draft.restriction(DELEGATION_RIGHTS.key).value;
+  const rights = draft.restriction(SHARING_RIGHTS.key).value;
   const noneTicked = Array.isArray(rights?.allowedValues) && rights.allowedValues.length === 0;
   return (
     <SettingsSection
@@ -19,15 +19,15 @@ export function DelegatesSection({ draft }: { draft: OrgPolicyDraft }) {
       description="Users can give a colleague read or read and write access to their mail folders, calendars and address books in one step, under Settings > Sharing. Stalwart doesn't let delegates send as the user; for an address several people send from, set up a shared mailbox."
     >
       <RestrictionRow draft={draft} def={DELEGATION} />
-      <RestrictionRow draft={draft} def={DELEGATION_RIGHTS} />
+      <RestrictionRow draft={draft} def={SHARING_RIGHTS} />
       {noneTicked && (
         <p className="text-xs text-destructive" role="status">
-          With neither ticked nothing is limited, so delegates can get both. Tick &quot;read&quot; to allow read access only.
+          With neither ticked nothing is limited, so users can give both. Tick &quot;read&quot; to allow read access only.
         </p>
       )}
       <p className="text-xs text-muted-foreground">
-        These apply to the Delegates dialog only. Sharing one folder, calendar or file from its own menu works as before, and Stalwart
-        itself enforces neither setting.
+        Both limit what Bulwark offers. Stalwart doesn&apos;t enforce them, so users can still share through other clients. Shared
+        mailboxes of groups are yours to manage in Stalwart.
       </p>
     </SettingsSection>
   );
diff --git a/components/settings/__tests__/share-collection-dialog-sharing-rights.test.tsx b/components/settings/__tests__/share-collection-dialog-sharing-rights.test.tsx
new file mode 100644
index 000000000..1ae4a235c
--- /dev/null
+++ b/components/settings/__tests__/share-collection-dialog-sharing-rights.test.tsx
@@ -0,0 +1,85 @@
+import { act, fireEvent, render, screen, waitFor, within } from '@testing-library/react';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { ShareCollectionDialog } from '../share-collection-dialog';
+import { MailboxShareDialog } from '@/components/layout/mailbox-share-dialog';
+import { usePolicyStore } from '@/stores/policy-store';
+import { presetRights, type AnyRights, type ShareKind } from '@/lib/jmap/share-rights';
+import type { IJMAPClient } from '@/lib/jmap/client-interface';
+import type { Mailbox } from '@/lib/jmap/types';
+
+// The admin's `sharingRights` without "write": every share dialog offers
+// the read presets only, and a grant that already gives more stays named but
+// can't be picked again.
+
+const initialPolicy = usePolicyStore.getState();
+afterEach(() => usePolicyStore.setState(initialPolicy, true));
+
+function readOnly() {
+  usePolicyStore.setState((state) => ({ policy: { ...state.policy, restrictions: { ...state.policy.restrictions, sharingRights: { allowedValues: ['read'] } } } }));
+}
+
+const client = {
+  getAccountId: () => 'me',
+  listPrincipals: vi.fn(async () => ({ principals: [], status: 'ok' as const })),
+  getPrincipals: vi.fn(async () => []),
+} as unknown as IJMAPClient;
+
+function renderKind(kind: ShareKind, shareWith: Record<string, AnyRights>) {
+  const onShare = vi.fn().mockResolvedValue(undefined);
+  render(<ShareCollectionDialog client={client} kind={kind} collectionName="X" shareWith={shareWith} ownAccountId="me" onShare={onShare} onClose={vi.fn()} />);
+  return onShare;
+}
+
+const offered = (select: HTMLElement) => within(select).getAllByRole('option')
+  .filter((o) => !(o as HTMLOptionElement).disabled)
+  .map((o) => (o as HTMLOptionElement).value);
+
+describe('sharingRights in the share dialogs', () => {
+  it.each([
+    ['mailbox', ['read', 'readWrite', 'manager']],
+    ['calendar', ['freeBusy', 'read', 'readWrite', 'manager']],
+    ['addressBook', ['read', 'readWrite', 'manager']],
+    ['file', ['read', 'readWrite', 'manager']],
+  ] as const)('offers every preset for a %s without a restriction', (kind, all) => {
+    renderKind(kind, { anna: presetRights(kind, 'read')! });
+    expect(offered(screen.getByRole('combobox'))).toEqual(all);
+    expect(screen.queryByText('org_locked')).toBeNull();
+  });
+
+  it.each([
+    ['mailbox', ['read']],
+    ['calendar', ['freeBusy', 'read']],
+    ['addressBook', ['read']],
+    ['file', ['read']],
+  ] as const)('offers only read presets for a %s without write, and says why', (kind, readOnlyPresets) => {
+    readOnly();
+    renderKind(kind, { anna: presetRights(kind, 'read')! });
+    expect(offered(screen.getByRole('combobox'))).toEqual(readOnlyPresets);
+    expect(screen.getByText('org_locked')).toBeInTheDocument();
+  });
+
+  it('keeps an existing write grant named but not pickable, and refuses to give write', async () => {
+    readOnly();
+    const onShare = renderKind('mailbox', { anna: presetRights('mailbox', 'readWrite')! });
+    const select = screen.getByRole('combobox') as HTMLSelectElement;
+    expect(select.value).toBe('readWrite');
+    expect((within(select).getByRole('option', { name: 'preset.readWrite' }) as HTMLOptionElement).disabled).toBe(true);
+    fireEvent.change(select, { target: { value: 'manager' } });
+    await act(async () => {});
+    expect(onShare).not.toHaveBeenCalled();
+    fireEvent.change(select, { target: { value: 'read' } });
+    await waitFor(() => expect(onShare).toHaveBeenCalledWith('anna', presetRights('mailbox', 'read')));
+  });
+
+  it('applies to the folder share dialog', async () => {
+    readOnly();
+    const mailboxClient = {
+      ...client,
+      getMailboxShareWith: vi.fn(async () => ({ anna: presetRights('mailbox', 'read') })),
+      setMailboxShare: vi.fn(async () => {}),
+    } as unknown as IJMAPClient;
+    render(<MailboxShareDialog client={mailboxClient} mailbox={{ id: 'a', name: 'Inbox', role: 'inbox' } as Mailbox} onClose={vi.fn()} />);
+    const select = await screen.findByRole('combobox');
+    expect(offered(select)).toEqual(['read']);
+  });
+});
diff --git a/components/settings/share-collection-dialog.tsx b/components/settings/share-collection-dialog.tsx
index 437da3f19..7ce4dce0f 100644
--- a/components/settings/share-collection-dialog.tsx
+++ b/components/settings/share-collection-dialog.tsx
@@ -10,6 +10,9 @@ import type { Principal, PrincipalDirectoryStatus } from "@/lib/jmap/types";
 import { detectPreset, presetRights, type AnyRights, type RolePreset, type ShareKind } from "@/lib/jmap/share-rights";
 import { loadPrincipalDirectory } from "@/lib/jmap/principal-directory";
 import { toast } from "@/stores/toast-store";
+import { useRestriction } from "@/hooks/use-restriction";
+import { allowedLevels } from "@/lib/delegation/delegation";
+import { OrgLockedNote } from "./org-locked-note";
 
 interface ShareCollectionDialogProps {
   client: IJMAPClient;
@@ -40,6 +43,9 @@ export function ShareCollectionDialog({
   const [search, setSearch] = useState("");
   const [savingId, setSavingId] = useState<string | null>(null);
   const [showAdd, setShowAdd] = useState(false);
+  // The admin's `sharingRights`: without write, only the read presets.
+  const sharingRights = useRestriction("sharingRights");
+  const writeAllowed = allowedLevels(sharingRights.allowedValues).includes("write");
 
   // Load principals on mount
   useEffect(() => {
@@ -79,8 +85,15 @@ export function ShareCollectionDialog({
     return () => document.removeEventListener("keydown", onKey);
   }, [onClose]);
 
+  const presetOptions: RolePreset[] = [
+    ...(kind === "calendar" ? ["freeBusy" as const] : []),
+    "read",
+    ...(writeAllowed ? ["readWrite" as const, "manager" as const] : []),
+  ];
+
   const handleSetRights = async (principalId: string, preset: RolePreset) => {
     if (preset === "custom") return; // custom is read-only here
+    if (!(presetOptions as readonly RolePreset[]).includes(preset)) return;
     const rights = presetRights(kind, preset);
     if (!rights) return;
     setSavingId(principalId);
@@ -136,9 +149,7 @@ export function ShareCollectionDialog({
     return Object.entries(shareWith || {}) as [string, AnyRights][];
   }, [shareWith]);
 
-  const presetOptions = kind === "calendar"
-    ? ["freeBusy", "read", "readWrite", "manager"] as const
-    : ["read", "readWrite", "manager"] as const;
+
 
   return (
     <div className="fixed inset-0 z-50 flex items-center justify-center">
@@ -166,6 +177,7 @@ export function ShareCollectionDialog({
 
         <div className="px-6 py-4 space-y-4 overflow-y-auto">
           <p className="text-sm text-muted-foreground">{t("description")}</p>
+          {!writeAllowed && <OrgLockedNote />}
 
           {sharedEntries.length === 0 && !showAdd && (
             <div className="text-sm text-muted-foreground italic py-4 text-center">
@@ -212,8 +224,9 @@ export function ShareCollectionDialog({
                         {presetOptions.map((p) => (
                           <option key={p} value={p}>{t(`preset.${p}`)}</option>
                         ))}
-                        {preset === "custom" && (
-                          <option value="custom">{t("preset.custom")}</option>
+                        {/* A grant the admin no longer lets users give stays named, but can't be picked. */}
+                        {!presetOptions.includes(preset) && (
+                          <option value={preset} disabled>{t(`preset.${preset}`)}</option>
                         )}
                       </select>
                       <ChevronDown className="w-3 h-3 absolute right-2 top-1/2 -translate-y-1/2 pointer-events-none text-muted-foreground" />
diff --git a/lib/admin/restriction-keys.ts b/lib/admin/restriction-keys.ts
index 0d11e4885..df4b49d04 100644
--- a/lib/admin/restriction-keys.ts
+++ b/lib/admin/restriction-keys.ts
@@ -43,7 +43,7 @@ export const RESTRICTION_KEYS: readonly RestrictionKeyDef[] = [
   { key: 'pushNotifyInboxOnly', label: 'Inbox-only Push Notifications', category: 'Notifications', type: 'boolean', page: 'policy' },
   { key: 'debugMode', label: 'Debug Mode', category: 'Advanced', type: 'boolean', page: 'policy' },
   { key: 'delegation', label: 'Delegates', description: 'Hide removes Settings > Sharing > Delegates, so users can no longer give someone access to mail, calendars and contacts in one step.', category: 'Sharing', type: 'boolean', page: 'org-sharing', modes: ['hidden'] },
-  { key: 'delegationRights', label: 'Rights delegates can get', description: 'Untick "write" and the Delegates dialog offers read access only.', category: 'Sharing', type: 'enum', allowedValues: ['read', 'write'], page: 'org-sharing', modes: ['allowedValues'] },
+  { key: 'sharingRights', label: 'Rights users can give', description: 'Untick "write" and every share dialog in Bulwark (folders, calendars, address books, files, Delegates) offers read access only.', category: 'Sharing', type: 'enum', allowedValues: ['read', 'write'], page: 'org-sharing', modes: ['allowedValues'] },
 ];
 
 export function restrictionKeysForPage(page: AdminPageId): RestrictionKeyDef[] {