diff --git a/web/src/App.tsx b/web/src/App.tsx
index 0d7c52e..fd8aab1 100644
--- a/web/src/App.tsx
+++ b/web/src/App.tsx
@@ -314,7 +314,7 @@ function AuthedApp() {
   // inbuxa AL-7: a locked account in view is named, with a padlock, in the
   // tab; a shared or group mailbox (MA-A) is named without one
   const viewingName = useSession((s) => (s.viewing ? s.session?.accounts[s.viewing]?.name : undefined));
-  const lockedInView = useViewingDelegation() !== null;
+  const lockedInView = useViewingDelegation()?.kind === "lock";
   useEffect(() => {
     setBaseTitle(viewingName ? `${lockedInView ? "🔒 " : ""}${viewingName} · ${appName}` : appName);
     setUnreadBadge(inboxUnread);
diff --git a/web/src/lib/delegation.ts b/web/src/lib/delegation.ts
index a7ca3f4..65d46c7 100644
--- a/web/src/lib/delegation.ts
+++ b/web/src/lib/delegation.ts
@@ -13,6 +13,12 @@ export type DelegationAccess = "read" | "organize" | "full";
 
 export interface Delegation {
   locked: boolean;
+  /**
+   * A locked account, or a shared mailbox such as support@ (MA-S). Both are
+   * reached as a delegate at an access level; only how they are shown
+   * differs. Absent from older servers, where it is always a lock.
+   */
+  kind: "lock" | "sharedMailbox";
   access: DelegationAccess;
   sendAs: boolean;
   /** UTC date the delegation ends, if it does. */
@@ -38,19 +44,20 @@ export function delegationOf(session: SessionLike | null, accountId: Id | null):
   const access: DelegationAccess = raw.access === "organize" || raw.access === "full" ? raw.access : "read";
   return {
     locked: true,
+    kind: raw.kind === "sharedMailbox" ? "sharedMailbox" : "lock",
     access,
     sendAs: raw.sendAs === true && access !== "read",
     until: typeof raw.until === "string" ? raw.until : null,
   };
 }
 
-/** Every locked account handed to the reader, by name. */
+/** Every locked account handed to the reader, by name. Shared mailboxes are listed by lib/sharedMail. */
 export function delegatedAccounts(session: SessionLike | null): DelegatedAccount[] {
   if (!session) return [];
   return Object.entries(session.accounts)
     .map(([id, account]) => {
       const delegation = delegationOf(session, id);
-      return delegation ? { id, name: account.name, delegation } : null;
+      return delegation?.kind === "lock" ? { id, name: account.name, delegation } : null;
     })
     .filter((a): a is DelegatedAccount => a !== null)
     .sort((a, b) => a.name.localeCompare(b.name));
diff --git a/web/src/lib/sharedMail.ts b/web/src/lib/sharedMail.ts
index 68568d4..22433af 100644
--- a/web/src/lib/sharedMail.ts
+++ b/web/src/lib/sharedMail.ts
@@ -1,6 +1,7 @@
 /**
  * Mail other people let the reader into (multi-account spec, MA-A): a group's
- * mailbox, or folders someone shared.
+ * mailbox, folders someone shared, or a shared mailbox an administrator
+ * assigned them to (MA-S).
  *
  * Either one arrives as another account in the session, `isPersonal: false`.
  * That alone proves nothing about mail -- the server advertises every
@@ -9,8 +10,10 @@
  * `Mailbox/get` answers with at least one mailbox has mail the reader can
  * open, and only those are offered.
  *
- * A locked account handed to the reader (AL-7) is listed by `delegation.ts`
- * instead, and left out here so it is never offered twice.
+ * A shared mailbox needs no asking: the server marks it, as a delegation of
+ * kind `sharedMailbox`, and it is mail by definition. A locked account handed
+ * to the reader (AL-7) is listed by `delegation.ts` instead, and left out
+ * here so it is never offered twice.
  */
 
 import { CAP, client } from "@/jmap/client";
@@ -28,7 +31,7 @@ type SessionLike = Pick<JmapSession, "accounts">;
 export function sharedMailCandidates(session: SessionLike | null): SharedMailAccount[] {
   if (!session) return [];
   return Object.entries(session.accounts)
-    .filter(([id, account]) => account.isPersonal === false && CAP.mail in (account.accountCapabilities ?? {}) && !delegationOf(session, id))
+    .filter(([id, account]) => account.isPersonal === false && CAP.mail in (account.accountCapabilities ?? {}) && delegationOf(session, id)?.kind !== "lock")
     .map(([id, account]) => ({ id, name: account.name }))
     .sort((a, b) => a.name.localeCompare(b.name));
 }
@@ -38,7 +41,9 @@ export async function findSharedMail(session: SessionLike | null): Promise<Share
   const candidates = sharedMailCandidates(session);
   const answers = await Promise.all(
     candidates.map((account) =>
-      client.call<GetResponse<Mailbox>>("Mailbox/get", { accountId: account.id, ids: null, properties: ["id"] }).then(
+      delegationOf(session, account.id)?.kind === "sharedMailbox"
+        ? Promise.resolve(account)
+        : client.call<GetResponse<Mailbox>>("Mailbox/get", { accountId: account.id, ids: null, properties: ["id"] }).then(
         (res) => (res.list.length > 0 ? account : null),
         () => null,
       ),
diff --git a/web/src/store/__tests__/delegated-accounts.test.ts b/web/src/store/__tests__/delegated-accounts.test.ts
index cb2d97e..5bcb8d7 100644
--- a/web/src/store/__tests__/delegated-accounts.test.ts
+++ b/web/src/store/__tests__/delegated-accounts.test.ts
@@ -70,7 +70,7 @@ afterEach(() => {
 describe("delegation", () => {
   it("is read only from the session's mark, never from a shared account's capabilities", () => {
     const session = sessionWith(delegated("organize", true));
-    expect(delegationOf(session, "locked")).toEqual({ locked: true, access: "organize", sendAs: true, until: null });
+    expect(delegationOf(session, "locked")).toEqual({ locked: true, kind: "lock", access: "organize", sendAs: true, until: null });
     expect(delegationOf(session, "shared")).toBeNull();
     expect(delegationOf(session, "own")).toBeNull();
     expect(delegatedAccounts(session).map((a) => a.id)).toEqual(["locked"]);
diff --git a/web/src/store/__tests__/shared-mail.test.ts b/web/src/store/__tests__/shared-mail.test.ts
index 3d29f65..6e52298 100644
--- a/web/src/store/__tests__/shared-mail.test.ts
+++ b/web/src/store/__tests__/shared-mail.test.ts
@@ -1,8 +1,9 @@
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import { CAP, client } from "@/jmap/client";
 import type { JmapSession } from "@/jmap/types";
-import { useSession } from "@/store/session";
+import { useSession, viewingDelegation } from "@/store/session";
 import { findSharedMail, sharedMailCandidates } from "@/lib/sharedMail";
+import { delegatedAccounts } from "@/lib/delegation";
 
 /**
  * MA-A: a group's mailbox, or folders someone shared, can be opened in place
@@ -36,6 +37,16 @@ const sessionWith = (extra: Record<string, unknown> = {}) =>
         isPersonal: false,
         accountCapabilities: { [CAP.mail]: {}, "urn:inbuxa:jmap": { delegation: { locked: true, access: "read", sendAs: false, until: null } } },
       },
+      // A shared mailbox an administrator assigned (MA-S): marked, so never asked about
+      desk: {
+        name: "desk@example.com",
+        isPersonal: false,
+        accountCapabilities: {
+          [CAP.mail]: {},
+          [CAP.calendars]: {},
+          "urn:inbuxa:jmap": { delegation: { locked: true, kind: "sharedMailbox", access: "organize", sendAs: true, until: null } },
+        },
+      },
       ...extra,
     },
     primaryAccounts: { [CAP.mail]: "own", [CAP.calendars]: "own", [CAP.contacts]: "own", [CAP.filenode]: "own" },
@@ -76,11 +87,12 @@ afterEach(() => {
 
 describe("shared mail", () => {
   it("considers only other people's accounts that advertise mail, leaving locked accounts to delegation", () => {
-    expect(sharedMailCandidates(sessionWith()).map((a) => a.id)).toEqual(["calendarOnly", "group"]);
+    expect(sharedMailCandidates(sessionWith()).map((a) => a.id)).toEqual(["calendarOnly", "desk", "group"]);
   });
 
   it("offers only accounts that answer with a mailbox", async () => {
-    expect((await findSharedMail(sessionWith())).map((a) => a.name)).toEqual(["support@example.com"]);
+    // The shared mailbox answers no Mailbox/get here, and is offered anyway
+    expect((await findSharedMail(sessionWith())).map((a) => a.name)).toEqual(["desk@example.com", "support@example.com"]);
   });
 
   it("can't be opened until it is found, and then shows mail only", async () => {
@@ -111,4 +123,14 @@ describe("shared mail", () => {
     expect(useSession.getState().viewing).toBeNull();
     expect(useSession.getState().delegationEnded).toBe("support@example.com");
   });
+
+  it("shows an assigned shared mailbox as shared, not locked, keeping its access level", async () => {
+    await useSession.getState().loadSharedMail();
+    expect(delegatedAccounts(useSession.getState().session).map((a) => a.id)).toEqual(["locked"]);
+    useSession.getState().view("desk");
+    expect(useSession.getState().viewing).toBe("desk");
+    expect(viewingDelegation()?.access).toBe("organize");
+    // Mail only, like any shared mailbox
+    expect(useSession.getState().viewAccountFor(CAP.calendars)).toBe("own");
+  });
 });
diff --git a/web/src/store/session.ts b/web/src/store/session.ts
index 5be4219..1a9582f 100644
--- a/web/src/store/session.ts
+++ b/web/src/store/session.ts
@@ -188,8 +188,8 @@ export const useSession = create<SessionState>((set, get) => ({
   viewAccountFor(cap) {
     const { session, viewing } = get();
     const viewed = viewing ? session?.accounts[viewing] : undefined;
-    // A shared or group mailbox in view is mail only (MA-A)
-    if (viewing && viewed && delegationOf(session, viewing) && cap in (viewed.accountCapabilities ?? {})) return viewing;
+    // A shared or group mailbox in view is mail only (MA-A, MA-S)
+    if (viewing && viewed && delegationOf(session, viewing)?.kind === "lock" && cap in (viewed.accountCapabilities ?? {})) return viewing;
     return ownAccountForCapability(session, cap);
   },
 }));
diff --git a/web/src/views/DelegatedBar.tsx b/web/src/views/DelegatedBar.tsx
index 2083926..1e685fd 100644
--- a/web/src/views/DelegatedBar.tsx
+++ b/web/src/views/DelegatedBar.tsx
@@ -38,6 +38,9 @@ export function DelegatedBar() {
         <Users size={15} aria-hidden />
         <span className="grow truncate">
           {t("Shared mailbox:")} <strong className="notranslate" translate="no">{shared.name}</strong>
+          {/* MA-S: one an administrator assigned says at what level */}
+          {delegation ? ` · ${accessText(delegation.access)}` : ""}
+          {delegation?.sendAs ? ` · ${t("You can send as this account")}` : ""}
         </span>
         <button type="button" onClick={back}>
           {t("Back to my mail")}