diff --git a/apps/web/utils/error.ts b/apps/web/utils/error.ts
index b72e11ee27..14b5ea5ba7 100644
--- a/apps/web/utils/error.ts
+++ b/apps/web/utils/error.ts
@@ -3,7 +3,6 @@ import {
   setUser,
 } from "@sentry/nextjs";
 import { APICallError, RetryError } from "ai";
-import type { z } from "zod";
 import { createScopedLogger } from "@/utils/logger";
 
 const logger = createScopedLogger("error");
@@ -117,6 +116,19 @@ export function isAWSThrottlingError(error: unknown): error is Error {
   );
 }
 
+export function isOutlookThrottlingError(error: unknown): boolean {
+  const err = error as Record<string, unknown>;
+  const code = err?.code as string | undefined;
+  const statusCode = err?.statusCode as number | undefined;
+  const message = err?.message as string | undefined;
+  return (
+    statusCode === 429 ||
+    code === "ApplicationThrottled" ||
+    code === "TooManyRequests" ||
+    (typeof message === "string" && /MailboxConcurrency/i.test(message))
+  );
+}
+
 export function isAICallError(error: unknown): error is APICallError {
   return APICallError.isInstance(error);
 }
@@ -131,6 +143,7 @@ export function isKnownApiError(error: unknown): boolean {
     isGmailInsufficientPermissionsError(error) ||
     isGmailRateLimitExceededError(error) ||
     isGmailQuotaExceededError(error) ||
+    isOutlookThrottlingError(error) ||
     (APICallError.isInstance(error) &&
       (isIncorrectOpenAIAPIKeyError(error) ||
         isInvalidOpenAIModelError(error) ||
@@ -174,6 +187,16 @@ export function checkCommonErrors(
     };
   }
 
+  if (isOutlookThrottlingError(error)) {
+    logger.warn("Outlook throttling error for url", { url });
+    return {
+      type: "Outlook Rate Limit",
+      message:
+        "Microsoft is temporarily limiting requests. Please try again shortly.",
+      code: 429,
+    };
+  }
+
   if (RetryError.isInstance(error) && isOpenAIRetryError(error)) {
     logger.warn("OpenAI quota exceeded for url", { url });
     return {
diff --git a/apps/web/utils/outlook/retry.test.ts b/apps/web/utils/outlook/retry.test.ts
index 053a95e7d7..066106a326 100644
--- a/apps/web/utils/outlook/retry.test.ts
+++ b/apps/web/utils/outlook/retry.test.ts
@@ -68,6 +68,26 @@ describe("isRetryableError", () => {
     expect(result.retryable).toBe(true);
   });
 
+  it("identifies ApplicationThrottled code as rate limit", () => {
+    const errorInfo = {
+      code: "ApplicationThrottled",
+      errorMessage: "Application is over its MailboxConcurrency limit.",
+    };
+    const result = isRetryableError(errorInfo);
+    expect(result.isRateLimit).toBe(true);
+    expect(result.retryable).toBe(true);
+  });
+
+  it("identifies MailboxConcurrency message as rate limit", () => {
+    const errorInfo = {
+      status: 429,
+      errorMessage: "MailboxConcurrency limit exceeded",
+    };
+    const result = isRetryableError(errorInfo);
+    expect(result.isRateLimit).toBe(true);
+    expect(result.retryable).toBe(true);
+  });
+
   it("identifies server errors", () => {
     for (const status of [502, 503, 504]) {
       const errorInfo = { status, errorMessage: "Server error" };
diff --git a/apps/web/utils/outlook/retry.ts b/apps/web/utils/outlook/retry.ts
index 9429f405fd..60f3c49b8e 100644
--- a/apps/web/utils/outlook/retry.ts
+++ b/apps/web/utils/outlook/retry.ts
@@ -13,7 +13,7 @@ interface ErrorInfo {
 
 /**
  * Retries a Microsoft Graph API operation when rate limits or temporary server errors are encountered
- * - Rate limits: 429, "TooManyRequests" code
+ * - Rate limits: 429, "TooManyRequests", "ApplicationThrottled", "MailboxConcurrency"
  * - Server errors: 502, 503, 504, "ServiceNotAvailable", "ServerBusy"
  */
 export async function withOutlookRetry<T>(
@@ -121,12 +121,13 @@ export function isRetryableError(errorInfo: ErrorInfo): {
 } {
   const { status, code, errorMessage } = errorInfo;
 
-  // Rate limit detection: 429 status or "TooManyRequests" code
+  // Rate limit detection: 429 status, throttling codes, or rate limit messages
   const isRateLimit =
     status === 429 ||
     code === "TooManyRequests" ||
+    code === "ApplicationThrottled" ||
     /rate limit/i.test(errorMessage) ||
-    /quota exceeded/i.test(errorMessage);
+    /MailboxConcurrency/i.test(errorMessage);
 
   // Temporary server errors that should be retried (502, 503, 504)
   const isServerError =
diff --git a/version.txt b/version.txt
index ec89d50dfe..50b5571c28 100644
--- a/version.txt
+++ b/version.txt
@@ -1 +1 @@
-v2.23.3
+v2.23.4