diff --git a/apps/web/utils/outlook/client.test.ts b/apps/web/utils/outlook/client.test.ts
index 70a4151fa9..8850fff763 100644
--- a/apps/web/utils/outlook/client.test.ts
+++ b/apps/web/utils/outlook/client.test.ts
@@ -1,5 +1,5 @@
 import { beforeEach, describe, expect, it, vi } from "vitest";
-import { Client } from "@microsoft/microsoft-graph-client";
+import { Client, MiddlewareFactory } from "@microsoft/microsoft-graph-client";
 import { saveTokens } from "@/utils/auth/save-tokens";
 import { createTestLogger } from "@/__tests__/helpers";
 import {
@@ -16,6 +16,10 @@ import {
 vi.mock("@microsoft/microsoft-graph-client", () => ({
   Client: {
     init: vi.fn(),
+    initWithMiddleware: vi.fn(),
+  },
+  MiddlewareFactory: {
+    getDefaultMiddlewareChain: vi.fn(),
   },
 }));
 
@@ -58,26 +62,52 @@ vi.mock("@/env", () => ({
 describe("outlook client emulator configuration", () => {
   beforeEach(() => {
     vi.clearAllMocks();
+    vi.mocked(MiddlewareFactory.getDefaultMiddlewareChain).mockReturnValue([
+      {
+        execute: vi.fn(),
+        setNext: vi.fn(),
+      },
+      {
+        execute: vi.fn(),
+        setNext: vi.fn(),
+      },
+    ]);
   });
 
-  it("passes emulator-aware Graph options into the client", () => {
+  it("authenticates requests to the HTTP emulator", async () => {
     createOutlookClient("emulator-token", createTestLogger());
 
     expect(getMicrosoftGraphClientOptions).toHaveBeenCalledWith(
       "emulator-token",
     );
-    expect(Client.init).toHaveBeenCalledWith({
-      authProvider: expect.any(Function),
+    expect(Client.initWithMiddleware).toHaveBeenCalledWith({
       baseUrl: "http://localhost:4003/",
       customHosts: new Set(["localhost"]),
       defaultVersion: "v1.0",
       fetchOptions: {
         headers: {
-          Authorization: "Bearer emulator-token",
           Prefer: 'IdType="ImmutableId"',
         },
       },
+      middleware: [expect.any(Object), expect.any(Object)],
     });
+
+    const options = vi.mocked(Client.initWithMiddleware).mock.calls[0]?.[0];
+    const middleware = Array.isArray(options?.middleware)
+      ? options.middleware
+      : [];
+    const request = {
+      request: "http://localhost:4003/v1.0/me",
+      options: { headers: {} },
+    };
+
+    middleware[0]?.setNext?.(middleware[1]!);
+    await middleware[0]?.execute(request);
+
+    expect(new Headers(request.options.headers).get("Authorization")).toBe(
+      "Bearer emulator-token",
+    );
+    expect(middleware[1]?.execute).toHaveBeenCalledWith(request);
   });
 
   it("uses the emulator authorize URL for linking", () => {
diff --git a/apps/web/utils/outlook/client.ts b/apps/web/utils/outlook/client.ts
index ba7c6bcfea..1b18f82ebf 100644
--- a/apps/web/utils/outlook/client.ts
+++ b/apps/web/utils/outlook/client.ts
@@ -1,4 +1,4 @@
-import { Client } from "@microsoft/microsoft-graph-client";
+import { Client, MiddlewareFactory } from "@microsoft/microsoft-graph-client";
 import type { User } from "@microsoft/microsoft-graph-types";
 import { saveTokens } from "@/utils/auth/save-tokens";
 import { cleanupInvalidTokens } from "@/utils/auth/cleanup-invalid-tokens";
@@ -27,6 +27,29 @@ export class OutlookClient {
     this.accessToken = accessToken;
     this.logger = logger;
     const graphClientOptions = getMicrosoftGraphClientOptions(accessToken);
+    const fetchOptions = {
+      headers: {
+        Prefer: 'IdType="ImmutableId"',
+      },
+    };
+    const emulatorAuthorization =
+      graphClientOptions.fetchOptions?.headers?.Authorization;
+
+    if (emulatorAuthorization) {
+      const middleware = MiddlewareFactory.getDefaultMiddlewareChain({
+        getAccessToken: async () => this.accessToken,
+      });
+      middleware[0] = createEmulatorAuthenticationMiddleware(
+        emulatorAuthorization,
+      );
+      this.client = Client.initWithMiddleware({
+        ...graphClientOptions,
+        fetchOptions,
+        middleware,
+      });
+      return;
+    }
+
     this.client = Client.init({
       authProvider: (done) => {
         done(null, this.accessToken);
@@ -35,12 +58,7 @@ export class OutlookClient {
       ...graphClientOptions,
       // Use immutable IDs to ensure message IDs remain stable
       // https://learn.microsoft.com/en-us/graph/outlook-immutable-id
-      fetchOptions: {
-        headers: {
-          ...(graphClientOptions.fetchOptions?.headers ?? {}),
-          Prefer: 'IdType="ImmutableId"',
-        },
-      },
+      fetchOptions,
     });
   }
 
@@ -256,5 +274,33 @@ export function getLinkingOAuth2Url() {
   return `${getMicrosoftOauthAuthorizeUrl()}?${params.toString()}`;
 }
 
+type GraphMiddleware = ReturnType<
+  typeof MiddlewareFactory.getDefaultMiddlewareChain
+>[number];
+
+function createEmulatorAuthenticationMiddleware(
+  authorization: string,
+): GraphMiddleware {
+  let nextMiddleware: GraphMiddleware | undefined;
+
+  return {
+    async execute(context) {
+      context.options ??= {};
+      const headers = new Headers(context.options.headers);
+      headers.set("Authorization", authorization);
+      context.options.headers = headers;
+
+      if (!nextMiddleware) {
+        throw new Error("Outlook emulator middleware is not configured");
+      }
+
+      await nextMiddleware.execute(context);
+    },
+    setNext(middleware) {
+      nextMiddleware = middleware;
+    },
+  };
+}
+
 // Helper types for common Microsoft Graph operations
 export type { Client as GraphClient };