all gmail stopped syncing to outlook 365 on my Macbook

Hi @Aya Abdulmajeed,

Thanks for using Microsoft product and posting in the Microsoft Q&A.

I understand you're experiencing a persistent issue where your Gmail account has stopped syncing with Outlook for Mac, even after you've tried removing and re-adding the account multiple times. This can definitely make it harder to keep track of your correspondence, and I appreciate you reaching out for assistance.

This is a known issue that can sometimes occur due to changes in Google's security protocols or a disruption in the authentication process between Outlook and your Gmail account. Let's work through a few steps to get your mail flowing again.

Solution 1: Use Google's Secure Sign-In

The most common and effective solution is to re-authenticate your account using the secure, native Google sign-in process. This ensures that Outlook has the correct permissions.

1. Remove the account again
2. Add the account back with the correct method:
   • Click the plus (+) button to add a new account.
   • Enter your full Gmail email address and click Continue.
   • You should see a new window pop up asking you to "Sign in with Google." Do not close this window. This is the critical step.
   • Follow the on-screen prompts to sign in to your Gmail account.
   • Google will ask you to grant permissions to Microsoft apps and services. Click Allow or Accept.

This process uses OAuth 2.0, which is the most secure and reliable way for Outlook to connect to your Gmail account.

Solution 2: Check Gmail's Security Settings

If the above steps don't work, we need to ensure that your Google account settings are not blocking Outlook.

1. Verify your account activity:
   • Go to your Google Account and navigate to the Security section.
   • Under Recent security activity, check for any "blocked sign-in attempt" warnings. If you see one, click on it and indicate that it was you. This may unblock the connection.
2. Generate an App Password (if you use 2-Step Verification):
   • If you have 2-Step Verification enabled on your Google account, you cannot use your regular password to sign in to Outlook.
   • Go to your Google Account and navigate to Security.
   • Under "How you sign in to Google," click on 2-Step Verification. You may need to sign in again.
   • Scroll down to the App passwords section.
   • Select Mail for the app and Mac for the device, then click Generate.
   • Google will provide you with a 16-character password. Copy this password immediately.
   • In Outlook, when adding your Gmail account, paste this 16-character password instead of your usual Gmail password.

Solution 3: Clear Outlook's Cache

A corrupted local cache can sometimes prevent syncing. Clearing the cache can force Outlook to re-download all your data.

1. Close Outlook completely.
2. In Finder, go to the Go menu
3. From the dropdown menu, select Go to Folder... (or press the keyboard shortcut Shift + Cmd + G).
4. In the text field that appears, type or paste the following path: ~/Library/Group Containers > Enter > UBF8T346G9.Office > Outlook > Outlook 15 Profiles > Main Profile > Data.
5. Locate the folder associated with your Gmail account (it will have your email address in the name). Drag this folder to your Desktop. Do not delete it yet, in case we need to restore it.
6. Re-open Outlook. It will be forced to re-sync all your Gmail data from the server, which should resolve any cache-related issues.

Solution 4: Verify IMAP Settings and Subscribed Folders

This approach ensures that all the necessary folders are correctly configured to sync between Outlook and your Gmail account.

• Open a web browser and sign in to your Gmail account.
• Click the Settings gear icon in the top right corner and select See all settings.
• Go to the "Forwarding and POP/IMAP" tab.
• In the "IMAP access" section, confirm that "IMAP is enabled" is selected. (Note: As of a recent update, for many personal Gmail accounts, this is now always on, but it's still good to verify).
• Check your "Folder size limits" and make sure it is not set to a small number, which could prevent a full sync.
• Navigate to the "Labels" tab. For each folder you want to see in Outlook (e.g., Inbox, Sent Mail, Drafts, your custom labels), ensure the "Show in IMAP" box is checked. This is a critical step, as unchecked folders will not sync to your email client.
• Click Save Changes at the bottom of the page if you made any adjustments.

Please try these solutions in the order provided and let me know if any of them help resolve the issue. If the problem persists after trying all these methods, we can explore further troubleshooting steps.

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Best regards   

Chloe L. | Microsoft Q&A Support Specialist