Gmail accounts added to Outlook rely on either IMAP or Google's own sync protocol, and most sync issues trace back to a setting on the Gmail side, not Outlook itself.
1. Confirm IMAP is enabled in Gmail
Log into Gmail in a browser, go to Settings > See all settings > Forwarding and POP/IMAP, and confirm IMAP is enabled. If it's off, Outlook can't sync at all regardless of how it's configured on your end.
2. Re-authenticate the account
Google periodically requires re-authentication for security, and an expired sign-in is one of the most common causes of silent sync failures. In Outlook, go to File > Account Settings, select the Gmail account, and look for a sign-in prompt or repair option.
3. Check folder sync settings
If specific folders (like Sent or Archive) aren't appearing, this is often because Gmail's IMAP folder mapping doesn't match Outlook's expectations by default. In Gmail's Forwarding and POP/IMAP settings, check the "Folder Size Limits" and label-to-folder behavior — Gmail treats labels as folders, which can cause mismatches.
Tip: if you use Gmail's "All Mail" label heavily, be aware it can cause duplicate-looking messages in Outlook since IMAP syncs it as its own folder alongside Inbox.
4. Check Gmail's "less secure app" / app password settings
Google has phased out simple password access for many account types in favor of app-specific passwords or OAuth. If your Outlook connection was set up with a basic password and stopped syncing, you may need to generate an app password specifically for Outlook via your Google Account security settings, or remove and re-add the account so it uses modern sign-in.
5. Remove and re-add the account
If targeted fixes don't resolve it, removing the Gmail account from Outlook entirely and re-adding it forces a fresh sync setup. Go to File > Account Settings > Email, select the account, remove it, then add it again through File > Add Account.
6. Check your internet connection's reliability
IMAP sync is more sensitive to intermittent connectivity than a quick page load — if your connection drops briefly and frequently, sync can stall in ways that look like a settings problem but aren't. Worth ruling out, especially on unstable WiFi.
The bottom line
Most Gmail-Outlook sync issues start on the Gmail side — IMAP settings or authentication — rather than anything wrong in Outlook itself. Confirm IMAP is on and re-authenticate before changing anything else.