diff --git a/.env.example b/.env.example
index 96245b1a0..f5f46bb39 100644
--- a/.env.example
+++ b/.env.example
@@ -30,7 +30,8 @@ JMAP_SERVER_URL=https://your-jmap-server.com
 # Prefer configuring this from the admin dashboard - the env form exists for
 # stateless deployments. An "oauth" block with both "clientId" and
 # "buttonLabel" gives that server its own sign-in button on the login page,
-# even while OAuth is off globally.
+# even while OAuth is off globally. "endSessionUrl" in the "oauth" block is
+# that server's OAUTH_END_SESSION_URL (see below).
 # JMAP_SERVERS=[{"id":"eu","label":"Europe","url":"https://eu.example.com","domains":["example.com"]},{"id":"us","label":"US","url":"https://us.example.com","oauth":{"clientId":"webmail-us"}}]
 
 # Pick the server automatically from the domain of the address the user types,
@@ -80,10 +81,19 @@ JMAP_SERVER_URL=https://your-jmap-server.com
 # OAUTH_ALLOW_PRIVATE_ENDPOINTS=true
 
 # Signing out of an SSO account also signs out of the identity provider,
-# through the end_session_endpoint it advertises (RP-initiated logout). Set to
-# false when the provider is shared with apps that should stay signed in.
+# through the end_session_endpoint it advertises or OAUTH_END_SESSION_URL
+# (RP-initiated logout). Set to false when the provider is shared with apps
+# that should stay signed in.
 # OAUTH_END_SESSION=false
 
+# The provider's logout URL, for providers whose discovery document has no
+# end_session_endpoint (Stalwart's built-in provider, for example). When set,
+# it is used instead of the discovered endpoint and gets the same parameters:
+# client_id, id_token_hint and post_logout_redirect_uri. Must be https.
+# Applies to OAUTH_ISSUER_URL's provider only; JMAP_SERVERS entries set their
+# own "endSessionUrl" in their "oauth" block.
+# OAUTH_END_SESSION_URL=https://your-idp.example.com/logout
+
 # Where the identity provider sends the browser after signing the user out.
 # Register it with the provider as a post-logout redirect URI first, or it
 # will refuse the logout. Unset: the provider shows its own signed-out page.
diff --git a/app/(main)/admin/_tabs/_jmap-servers-section.tsx b/app/(main)/admin/_tabs/_jmap-servers-section.tsx
index 2f0c531e0..3dab7f75d 100644
--- a/app/(main)/admin/_tabs/_jmap-servers-section.tsx
+++ b/app/(main)/admin/_tabs/_jmap-servers-section.tsx
@@ -20,6 +20,7 @@ interface RowDraft {
   oauthIssuerUrl: string;
   oauthClientSecret: string;
   oauthButtonLabel: string;
+  oauthEndSessionUrl: string;
   oauthExpanded: boolean;
 }
 
@@ -33,7 +34,8 @@ function entryToDraft(e: JmapServerEntry): RowDraft {
     oauthIssuerUrl: e.oauth?.issuerUrl ?? '',
     oauthClientSecret: e.oauth?.clientSecret ?? '',
     oauthButtonLabel: e.oauth?.buttonLabel ?? '',
-    oauthExpanded: !!(e.oauth && (e.oauth.clientId || e.oauth.issuerUrl || e.oauth.clientSecret)),
+    oauthEndSessionUrl: e.oauth?.endSessionUrl ?? '',
+    oauthExpanded: !!(e.oauth && (e.oauth.clientId || e.oauth.issuerUrl || e.oauth.clientSecret || e.oauth.endSessionUrl)),
   };
 }
 
@@ -49,12 +51,14 @@ function draftToEntry(d: RowDraft): JmapServerEntry | null {
   const issuerUrl = d.oauthIssuerUrl.trim().replace(/\/+$/, '');
   const clientSecret = d.oauthClientSecret;
   const buttonLabel = d.oauthButtonLabel.trim();
-  const oauth = clientId || issuerUrl || clientSecret
+  const endSessionUrl = d.oauthEndSessionUrl.trim();
+  const oauth = clientId || issuerUrl || clientSecret || endSessionUrl
     ? {
         ...(clientId ? { clientId } : {}),
         ...(issuerUrl ? { issuerUrl } : {}),
         ...(clientSecret ? { clientSecret } : {}),
         ...(buttonLabel ? { buttonLabel } : {}),
+        ...(endSessionUrl ? { endSessionUrl } : {}),
       }
     : undefined;
   return {
@@ -76,6 +80,7 @@ function emptyDraft(): RowDraft {
     oauthIssuerUrl: '',
     oauthClientSecret: '',
     oauthButtonLabel: '',
+    oauthEndSessionUrl: '',
     oauthExpanded: false,
   };
 }
@@ -268,6 +273,19 @@ export function JmapServersSection({ value, source, onChange, onRevert }: Props)
                     With a client ID, this label gives the server its own sign-in button on the login page, whichever server is selected and even while OAuth is off globally.
                   </p>
                 </div>
+                <div className="sm:col-span-3">
+                  <label className="block text-[11px] font-medium text-muted-foreground mb-1">Provider logout URL</label>
+                  <input
+                    type="url"
+                    value={d.oauthEndSessionUrl}
+                    onChange={(e) => update(i, { oauthEndSessionUrl: e.target.value })}
+                    placeholder="https://auth.example.com/logout"
+                    className="h-8 w-full rounded-md border border-input bg-background px-2 text-sm text-foreground focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring"
+                  />
+                  <p className="mt-1 text-[11px] text-muted-foreground">
+                    Where signing out sends the browser to end the provider&apos;s session, instead of the end_session_endpoint from discovery. Set it for providers that advertise none, such as Stalwart. Must be https.
+                  </p>
+                </div>
               </div>
             )}
           </div>
diff --git a/app/(main)/admin/_tabs/auth.tsx b/app/(main)/admin/_tabs/auth.tsx
index 7d28e969b..730111def 100644
--- a/app/(main)/admin/_tabs/auth.tsx
+++ b/app/(main)/admin/_tabs/auth.tsx
@@ -296,7 +296,8 @@ export function AuthTab() {
 
       <Section title="Single Sign-On">
         <Toggle label="Auto SSO" description="Automatically redirect to SSO provider on load" configKey="autoSsoEnabled" value={currentValue('autoSsoEnabled') as boolean} source={config.autoSsoEnabled?.source} onChange={handleChange} onRevert={handleRevert} />
-        <Toggle label="End provider session on sign-out" description="Signing out of an SSO account also signs out of the identity provider, when it advertises an end_session_endpoint. Turn off if the provider is shared with apps that should stay signed in." configKey="oauthEndSession" value={currentValue('oauthEndSession') as boolean} source={config.oauthEndSession?.source} onChange={handleChange} onRevert={handleRevert} />
+        <Toggle label="End provider session on sign-out" description="Signing out of an SSO account also signs out of the identity provider, when it advertises an end_session_endpoint or a logout URL is set below. Turn off if the provider is shared with apps that should stay signed in." configKey="oauthEndSession" value={currentValue('oauthEndSession') as boolean} source={config.oauthEndSession?.source} onChange={handleChange} onRevert={handleRevert} />
+        <Text label="Provider logout URL" description="For providers whose discovery has no end_session_endpoint, such as Stalwart. Used instead of the discovered endpoint when set, with the same parameters. Must be https. Applies to the global OAuth settings; servers in the server list set their own." configKey="oauthEndSessionUrl" value={currentValue('oauthEndSessionUrl') as string} source={config.oauthEndSessionUrl?.source} onChange={handleChange} onRevert={handleRevert} placeholder="https://auth.example.com/logout" />
         <Text label="Post-logout redirect URI" description="Where the provider sends users after signing them out. Register it with the provider as a post-logout redirect URI first, or it will refuse the logout. Leave blank to stay on the provider's signed-out page." configKey="oauthPostLogoutRedirectUri" value={currentValue('oauthPostLogoutRedirectUri') as string} source={config.oauthPostLogoutRedirectUri?.source} onChange={handleChange} onRevert={handleRevert} placeholder="https://mail.example.com/en/login" />
       </Section>
 
diff --git a/app/api/auth/token/route.ts b/app/api/auth/token/route.ts
index 963179dc8..0631a5399 100644
--- a/app/api/auth/token/route.ts
+++ b/app/api/auth/token/route.ts
@@ -70,17 +70,26 @@ async function revokeRefreshToken(token: string, serverId: string | null, metada
   }
 }
 
-/** The provider logout URL for a slot being signed out, or null when there is none to visit. */
+/**
+ * The provider logout URL for a slot being signed out, or null when there is
+ * none to visit. A logout URL the admin configured (#1279) goes before the
+ * discovered one: it is there for providers that advertise none, such as
+ * Stalwart, and for a logout page shared with other apps, which must keep
+ * working once the provider starts advertising its own.
+ */
 function endSessionUrlFor(metadata: OAuthMetadata | null, serverId: string | null, idToken: string | undefined): string | null {
-  if (!metadata?.end_session_endpoint || !isEndSessionEnabled()) return null;
+  if (!isEndSessionEnabled()) return null;
   let clientId: string;
+  let configuredEndpoint: string | undefined;
   try {
-    ({ clientId } = getRequiredConfig(serverId));
+    ({ clientId, endSessionUrl: configuredEndpoint } = getRequiredConfig(serverId));
   } catch {
     return null;
   }
+  const endpoint = configuredEndpoint || metadata?.end_session_endpoint;
+  if (!endpoint) return null;
   return buildEndSessionUrl({
-    endpoint: metadata.end_session_endpoint,
+    endpoint,
     clientId,
     idToken,
     postLogoutRedirectUri: getPostLogoutRedirectUri(),
@@ -265,7 +274,7 @@ export async function PUT(request: NextRequest) {
 /**
  * Revoke a slot's refresh token and clear its token cookies. With
  * `endSession`, also returns the URL that ends the provider's session, or null
- * when the provider has no usable end_session_endpoint.
+ * when there is no usable logout URL.
  */
 async function signOutSlot(
   cookieStore: CookieStore,
diff --git a/lib/__tests__/oauth-issuer-precedence.test.ts b/lib/__tests__/oauth-issuer-precedence.test.ts
index 58d8ad9a9..5858d3bf3 100644
--- a/lib/__tests__/oauth-issuer-precedence.test.ts
+++ b/lib/__tests__/oauth-issuer-precedence.test.ts
@@ -25,6 +25,13 @@ const SERVERS = [
     url: 'https://mx3.example.com',
     oauth: { issuerUrl: 'https://idp3.example.com' },
   },
+  {
+    id: 'mx4',
+    label: 'Server 4',
+    url: 'https://mx4.example.com',
+    oauth: { endSessionUrl: ' https://mx4.example.com/logout/ ' },
+  },
+  { id: 'mx5', label: 'Server 5', url: 'https://mx5.example.com', oauth: { endSessionUrl: 'logout' } },
 ];
 
 vi.mock('@/lib/admin/config-manager', () => ({
@@ -64,3 +71,30 @@ describe('SSO discovery issuer precedence (#952)', () => {
     expect(getRequiredConfig('unknown').discoveryUrl).toBe('https://idp1.example.com');
   });
 });
+
+describe('configured end-session URL precedence (#1279)', () => {
+  beforeEach(() => {
+    vi.stubEnv('JMAP_SERVER_URL', 'https://mx1.example.com');
+    vi.stubEnv('OAUTH_CLIENT_ID', 'client');
+    vi.stubEnv('OAUTH_END_SESSION_URL', 'https://idp1.example.com/logout');
+  });
+
+  afterEach(() => {
+    vi.unstubAllEnvs();
+  });
+
+  it('uses the selected server\'s own logout URL, as written', () => {
+    // A trailing slash is part of some providers' logout path.
+    expect(getRequiredConfig('mx4').endSessionUrl).toBe('https://mx4.example.com/logout/');
+  });
+
+  it('does not give a server entry the global logout URL', () => {
+    expect(getRequiredConfig('mx2').endSessionUrl).toBeUndefined();
+    expect(getRequiredConfig('mx5').endSessionUrl).toBeUndefined();
+  });
+
+  it('uses the global logout URL when no server entry matched', () => {
+    expect(getRequiredConfig(null).endSessionUrl).toBe('https://idp1.example.com/logout');
+    expect(getRequiredConfig('unknown').endSessionUrl).toBe('https://idp1.example.com/logout');
+  });
+});
diff --git a/lib/__tests__/oauth-token-route.test.ts b/lib/__tests__/oauth-token-route.test.ts
index b915acb54..d220afc01 100644
--- a/lib/__tests__/oauth-token-route.test.ts
+++ b/lib/__tests__/oauth-token-route.test.ts
@@ -611,6 +611,52 @@ describe('oauth token route - sign-out (#905)', () => {
     expect(body.end_session_url).toBeUndefined();
   });
 
+  // Stalwart's built-in provider advertises no end_session_endpoint (#1279).
+  it('builds the provider logout from the configured URL when discovery has none', async () => {
+    seedSlot(0);
+    getMetadata.mockResolvedValue({ ...KEYCLOAK, end_session_endpoint: undefined });
+    getRequiredConfig.mockReturnValue({ clientId: 'webmail', endSessionUrl: 'https://mail.example.org/logout/' });
+    configValues.oauthPostLogoutRedirectUri = 'https://mail.example.com/en/login';
+
+    const { body } = await callRoute('DELETE', { slot: '0', end_session: 'true' });
+
+    const url = new URL(body.end_session_url as string);
+    expect(`${url.origin}${url.pathname}`).toBe('https://mail.example.org/logout/');
+    expect(url.searchParams.get('client_id')).toBe('webmail');
+    expect(url.searchParams.get('id_token_hint')).toBe(ID_TOKEN);
+    expect(url.searchParams.get('post_logout_redirect_uri')).toBe('https://mail.example.com/en/login');
+  });
+
+  it('prefers the configured logout URL over the discovered one', async () => {
+    seedSlot(0);
+    getRequiredConfig.mockReturnValue({ clientId: 'webmail', endSessionUrl: 'https://sso.example.com/logout' });
+
+    const { body } = await callRoute('DELETE', { slot: '0', end_session: 'true' });
+
+    const url = new URL(body.end_session_url as string);
+    expect(`${url.origin}${url.pathname}`).toBe('https://sso.example.com/logout');
+  });
+
+  it('does not use the configured logout URL when the admin turned provider logout off', async () => {
+    seedSlot(0);
+    getRequiredConfig.mockReturnValue({ clientId: 'webmail', endSessionUrl: 'https://sso.example.com/logout' });
+    configValues.oauthEndSession = false;
+
+    const { body } = await callRoute('DELETE', { slot: '0', end_session: 'true' });
+
+    expect(body.end_session_url).toBeUndefined();
+  });
+
+  it('does not offer a configured logout URL over plain http', async () => {
+    seedSlot(0);
+    getMetadata.mockResolvedValue({ ...KEYCLOAK, end_session_endpoint: undefined });
+    getRequiredConfig.mockReturnValue({ clientId: 'webmail', endSessionUrl: 'http://mail.example.org/logout' });
+
+    const { body } = await callRoute('DELETE', { slot: '0', end_session: 'true' });
+
+    expect(body.end_session_url).toBeUndefined();
+  });
+
   it.each([
     ['non-https', 'http://id.example.com/logout'],
     ['malformed', 'not a url'],
diff --git a/lib/admin/jmap-servers.ts b/lib/admin/jmap-servers.ts
index aa79b727a..d78f05d60 100644
--- a/lib/admin/jmap-servers.ts
+++ b/lib/admin/jmap-servers.ts
@@ -8,6 +8,8 @@ export interface JmapServerOAuthConfig {
   clientSecret?: string;
   /** Text of this server's sign-in button, e.g. "Sign in with Google"; the generic SSO label otherwise. */
   buttonLabel?: string;
+  /** The provider's logout URL, used instead of a discovered end_session_endpoint (#1279). Never sent to the browser. */
+  endSessionUrl?: string;
 }
 
 export interface JmapServerEntry {
@@ -82,12 +84,15 @@ export function parseJmapServers(raw: unknown): JmapServerEntry[] {
       const issuerUrl = typeof o.issuerUrl === 'string' ? trimUrl(o.issuerUrl) : '';
       const clientSecret = typeof o.clientSecret === 'string' ? o.clientSecret : '';
       const buttonLabel = typeof o.buttonLabel === 'string' ? o.buttonLabel.trim().slice(0, 64) : '';
-      if (clientId || issuerUrl || clientSecret) {
+      // Kept as written: some providers' logout path ends in a slash.
+      const endSessionUrl = typeof o.endSessionUrl === 'string' ? o.endSessionUrl.trim() : '';
+      if (clientId || issuerUrl || clientSecret || endSessionUrl) {
         oauth = {};
         if (clientId) oauth.clientId = clientId;
         if (issuerUrl && isHttpUrl(issuerUrl)) oauth.issuerUrl = issuerUrl;
         if (clientSecret) oauth.clientSecret = clientSecret;
         if (buttonLabel) oauth.buttonLabel = buttonLabel;
+        if (endSessionUrl && isHttpUrl(endSessionUrl)) oauth.endSessionUrl = endSessionUrl;
       }
     }
     out.push({
diff --git a/lib/admin/types.ts b/lib/admin/types.ts
index 8e17ce6f0..758f00125 100644
--- a/lib/admin/types.ts
+++ b/lib/admin/types.ts
@@ -266,6 +266,11 @@ export const CONFIG_ENV_MAP: Record<string, { envVar: string; fileEnvVar?: strin
   // through its end_session_endpoint (#905). Off keeps the provider signed in,
   // for providers shared with other apps that should stay signed in.
   oauthEndSession: { envVar: 'OAUTH_END_SESSION', type: 'boolean', defaultValue: true },
+  // The provider's logout URL, for providers whose discovery document has no
+  // end_session_endpoint (#1279). Used instead of the discovered one when set.
+  // Applies to the global provider only; JMAP_SERVERS entries set their own
+  // oauth.endSessionUrl.
+  oauthEndSessionUrl: { envVar: 'OAUTH_END_SESSION_URL', type: 'url', defaultValue: '' },
   // Where the provider sends the browser after ending its session. Must be
   // registered with the provider as a post-logout redirect URI. Empty = none
   // is sent and the provider shows its own signed-out page.
diff --git a/lib/oauth/end-session.ts b/lib/oauth/end-session.ts
index 05e4caf11..40022bb6a 100644
--- a/lib/oauth/end-session.ts
+++ b/lib/oauth/end-session.ts
@@ -11,7 +11,9 @@ import { fitsSetCookieBudget } from '@/lib/oauth/set-cookie-budget';
  * "Sign in with SSO" silently signs the same person back in. Signing out
  * therefore finishes with a top-level navigation to the provider's
  * end_session_endpoint, carrying the parameters it needs to identify the
- * session and the client.
+ * session and the client. Providers that advertise none get a logout URL
+ * from the admin instead (OAUTH_END_SESSION_URL or a server's
+ * oauth.endSessionUrl, #1279), and it is sent the same parameters.
  */
 
 export const ID_TOKEN_COOKIE = 'jmap_idt';
@@ -106,7 +108,7 @@ export function getPostLogoutRedirectUri(): string | undefined {
 
 /**
  * The URL to navigate the browser to so the provider ends its session, or
- * null when the discovered endpoint is unusable.
+ * null when the discovered or configured endpoint is unusable.
  *
  * `client_id` is always sent: providers use it to validate the redirect URI
  * and to find the session when no id token is at hand. `id_token_hint` is sent
diff --git a/lib/oauth/token-exchange.ts b/lib/oauth/token-exchange.ts
index b05742527..8c6c27598 100644
--- a/lib/oauth/token-exchange.ts
+++ b/lib/oauth/token-exchange.ts
@@ -118,7 +118,12 @@ export function getRequiredConfig(serverId?: string | null, options?: ClientConf
   if (issuerUrl !== undefined && issuerUrl !== '' && !issuerUrl.trim()) {
     logger.warn('OAUTH_ISSUER_URL is set but empty, falling back to JMAP_SERVER_URL for discovery');
   }
-  return { clientId, serverUrl, discoveryUrl, serverId: entry?.id };
+  // Belongs to the same provider as the issuer, so the same rule applies:
+  // the global OAUTH_END_SESSION_URL only without a server entry (#1279).
+  const endSessionUrl = entry
+    ? entry.oauth?.endSessionUrl
+    : (configManager.get<string>('oauthEndSessionUrl', '') || process.env.OAUTH_END_SESSION_URL)?.trim() || undefined;
+  return { clientId, serverUrl, discoveryUrl, serverId: entry?.id, endSessionUrl };
 }
 
 export function getClientSecret(serverId?: string | null): string {