diff --git a/src/api/__tests__/live-stalwart-auth.test.ts b/src/api/__tests__/live-stalwart-auth.test.ts
index 7dab439b..7529bf7a 100644
--- a/src/api/__tests__/live-stalwart-auth.test.ts
+++ b/src/api/__tests__/live-stalwart-auth.test.ts
@@ -65,6 +65,7 @@ import {
   TotpLoginError,
 } from '../../lib/totp-login';
 import { describeLoginError } from '../../lib/login-errors';
+import { fetchMailQuota, serverSupportsQuota, toMailQuota } from '../quota';
 import { discoverOAuthMetadata, loginWithPkce, pkceScopes, revokeRefreshToken } from '../../lib/oauth-native';
 import {
   HANDOFF_REDIRECT_URI,
@@ -389,6 +390,28 @@ live('live Stalwart sign-in', () => {
     expect(copy.detail).toMatch(/password and code were accepted/);
   }, 30_000);
 
+  it('reads the storage quota the way Settings shows it, on both (#1242)', async () => {
+    const client = new JMAPClient();
+    await client.connect(SERVER, USER, PASS);
+    useSingleton(client);
+    if (!serverSupportsQuota()) return;
+    const res = await client.request([['Quota/get', { accountId: client.accountId }, '0']], [
+      'urn:ietf:params:jmap:core',
+      'urn:ietf:params:jmap:quota',
+    ]);
+    const [name, body] = res.methodResponses[0] as unknown as [string, { list: Array<Record<string, number | null>> }];
+    expect(name).toBe('Quota/get');
+    const shown = await fetchMailQuota();
+    expect(shown).toEqual(toMailQuota(body.list as never));
+    if (shown) {
+      const raw = body.list.find((q) => q.resourceType === ('octets' as unknown as number))!;
+      // Never above a softLimit the server set below its hardLimit.
+      if (typeof raw.softLimit === 'number' && raw.softLimit > 0 && typeof raw.hardLimit === 'number' && raw.softLimit < raw.hardLimit) {
+        expect(shown.total).toBe(raw.softLimit);
+      }
+    }
+  });
+
   it('account security with the password (Basic) works on both', async () => {
     const client = new JMAPClient();
     await client.connect(SERVER, USER, PASS);
diff --git a/src/api/__tests__/quota.test.ts b/src/api/__tests__/quota.test.ts
new file mode 100644
index 00000000..2eca136e
--- /dev/null
+++ b/src/api/__tests__/quota.test.ts
@@ -0,0 +1,30 @@
+import { describe, it, expect, vi } from 'vitest';
+
+// Storage usage counted against hardLimit even where the server set a lower
+// softLimit, from which writes already fail (RFC 9425 4.1, webmail #1242).
+
+const quotas: Record<string, unknown>[] = [];
+vi.mock('../jmap-client', () => ({
+  jmapClient: {
+    accountId: 'a1',
+    currentSession: { capabilities: { 'urn:ietf:params:jmap:quota': {} } },
+    request: vi.fn(async () => ({ methodResponses: [['Quota/get', { list: quotas }, '0']] })),
+  },
+}));
+
+import { fetchMailQuota, toMailQuota } from '../quota';
+
+describe('mail quota', () => {
+  it('counts against softLimit when it is below hardLimit (#1242)', async () => {
+    quotas.splice(0, quotas.length, {
+      id: 'q', resourceType: 'octets', scope: 'account', used: 900, softLimit: 1000, hardLimit: 1200, warnLimit: 800,
+    });
+    await expect(fetchMailQuota()).resolves.toEqual({ used: 900, total: 1000, hardLimit: 1200, warnAt: 800 });
+  });
+
+  it('keeps hardLimit when there is no lower softLimit', () => {
+    expect(toMailQuota([{ id: 'q', resourceType: 'octets', used: 1, hardLimit: 10, softLimit: null }])).toEqual({ used: 1, total: 10 });
+    expect(toMailQuota([{ id: 'q', resourceType: 'octets', used: 1, hardLimit: 10, softLimit: 20 }])).toEqual({ used: 1, total: 10 });
+    expect(toMailQuota([{ id: 'q', resourceType: 'mail', used: 1, limit: 5 }])).toEqual({ used: 1, total: 5 });
+  });
+});
diff --git a/src/api/quota.ts b/src/api/quota.ts
index 6eb6d870..23c58534 100644
--- a/src/api/quota.ts
+++ b/src/api/quota.ts
@@ -8,8 +8,8 @@ interface JMAPQuota {
   resourceType?: string;
   used?: number;
   hardLimit?: number;
-  warnLimit?: number;
-  softLimit?: number;
+  warnLimit?: number | null;
+  softLimit?: number | null;
   // pre-RFC shape
   limit?: number;
   scope?: string;
@@ -19,7 +19,38 @@ interface JMAPQuota {
 
 export interface MailQuota {
   used: number;
+  /**
+   * The limit the user works against: softLimit when the server sets one
+   * below hardLimit, since writes start failing there (RFC 9425 4.1,
+   * webmail #1242). Otherwise hardLimit.
+   */
   total: number;
+  /** hardLimit, only when it is above `total` (inbound mail still lands up to it). */
+  hardLimit?: number;
+  /** warnLimit, only when it is below `total`. */
+  warnAt?: number;
+}
+
+const positive = (n: number | null | undefined): n is number =>
+  typeof n === 'number' && Number.isFinite(n) && n > 0;
+
+/** Picks the mail storage quota out of a Quota/get list (webmail lib/quota.ts toStorageQuota). */
+export function toMailQuota(quotas: JMAPQuota[]): MailQuota | null {
+  const coversMail = (q: JMAPQuota) =>
+    !q.types?.length || q.types.some((t) => t === 'Email' || t === 'Mail');
+  // Storage quotas use resourceType "octets" (Stalwart, scope "account");
+  // older servers used the pre-RFC "mail" shape.
+  const q =
+    quotas.find((x) => x.resourceType === 'octets' && coversMail(x))
+    || quotas.find((x) => x.resourceType === 'mail' || x.scope === 'mail');
+  if (!q) return null;
+  const hard = q.hardLimit ?? q.limit ?? 0;
+  const soft = positive(q.softLimit) && (!positive(hard) || q.softLimit < hard) ? q.softLimit : undefined;
+  const total = soft ?? hard;
+  const quota: MailQuota = { used: q.used ?? 0, total };
+  if (soft !== undefined && positive(hard)) quota.hardLimit = hard;
+  if (positive(q.warnLimit) && (!positive(total) || q.warnLimit < total)) quota.warnAt = q.warnLimit;
+  return quota;
 }
 
 export function serverSupportsQuota(): boolean {
@@ -40,15 +71,7 @@ export async function fetchMailQuota(): Promise<MailQuota | null> {
     );
     const [name, body] = res.methodResponses[0] ?? [];
     if (name !== 'Quota/get') return null;
-    const quotas = (body?.list ?? []) as JMAPQuota[];
-    const coversMail = (q: JMAPQuota) =>
-      !q.types?.length || q.types.some((t) => t === 'Email' || t === 'Mail');
-    const mailQuota =
-      quotas.find((q) => q.resourceType === 'octets' && coversMail(q))
-      || quotas.find((q) => q.resourceType === 'mail' || q.scope === 'mail');
-    if (!mailQuota) return null;
-    const total = mailQuota.hardLimit ?? mailQuota.limit ?? 0;
-    return { used: mailQuota.used ?? 0, total };
+    return toMailQuota((body?.list ?? []) as JMAPQuota[]);
   } catch {
     return null;
   }