Resolving “Account exceeds bandwidth limits”

When opening an email client or trying to check messages via IMAP or webmail, you may encounter an explicit alert: “Account exceeds bandwidth limits,” “Temporary Lockout,” or “HTTP 429: Too Many Requests.” In mail clients like Apple Mail, Outlook, or Thunderbird, the connection simply drops or keeps prompting for credentials even though your username and password are correct.

Quick Answer

Google places temporary lockouts on accounts that exceed its daily IMAP, POP, or web data transfer limits (usually 2,500 MB/day for downloads or 500 MB/day for uploads). To fix it, stop all running mail applications on your devices, wait between 1 and 24 hours for the counter to reset, and cap your IMAP folder synchronization sizes.

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What the Limit Means

To protect its shared infrastructure from denial-of-service disruptions and automated scraping, Google monitors how much raw data flows in and out of each Gmail or Google Workspace mailbox.

When your account triggers an “Account exceeds bandwidth limits” lockout, you have hit one of Google’s rolling data-transfer thresholds:

Protocol / Vector	Rolling Daily Limit	Typical Action Triggering Limit
IMAP Download	~2,500 MB / day	Setting up a new mail client with full historical sync
IMAP Upload	~500 MB / day	Moving large mail archives or PSTs into Gmail via drag-and-drop
POP Download	~1,250 MB / day	Repeated full-inbox POP downloads across multiple devices
Web Client Interface	Variable heuristic limits	Constantly refreshing multiple large search queries

The lockout is an automated protective cooldown. It prevents all external clients from downloading or uploading new data for anywhere from 1 hour up to 24 hours, depending on how far above the threshold the account climbed.

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What Causes the Bandwidth Trip?

Bandwidth Limit Trip
│
├── Did you recently add this account to a new phone or computer?
│   ├── YES ──► Initial bulk synchronization of the "All Mail" archive.
│   └── NO  ──► Background sync loop or concurrent client overload.
│
├── Are multiple clients checking the account simultaneously?
│   ├── YES ──► Aggregated polling frequency exceeded API caps.
│   └── NO  ──► Local data corruption forcing repeated re-downloads.

1. Synchronizing the [Gmail]/All Mail Folder: The default IMAP profile in many mail clients indexes every single folder, including All Mail. If your account contains 15 GB of mail and you configure a new device, the client tries to download everything immediately. It will hit the 2,500 MB cap in under an hour.
2. Sync Loops from Corrupted Local Cache: If a local .ost or .mbox file becomes corrupted, the client may fail to write incoming messages to disk, discard the batch, and request the exact same 500 MB of data repeatedly throughout the day.
3. Too Many Connected Devices Polling Simultaneously: If you run Outlook on a laptop, Apple Mail on an iPad, the native mail client on an iPhone, and an automated backup script on a server, their simultaneous background polling can consume your daily quota.
4. Third-Party Email Scrapers and Automation: Third-party CRM tools, automated backup software, or migration utilities running multiple threads can trigger bandwidth blocks within minutes.

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Diagnostic and Recovery Steps

Step 1: Halt All Mail Connections Immediately

Continuing to check mail while under a bandwidth block extends the lockout window.

1. Close desktop email clients (Outlook, Thunderbird, Apple Mail) on all personal and work computers.
2. Put mobile devices into airplane mode, or temporarily turn off mail syncing under your phone’s settings (Settings > Mail > Accounts > Account > Toggle Mail Off).
3. Log into Gmail using a standard desktop web browser. Webmail often remains accessible during an IMAP-specific lockout.

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Step 2: Identify and Disconnect Third-Party Apps

Third-party services running in the background may be consuming your quota without your knowledge:

1. In your browser, open your Google Account Permissions.
2. Look through Third-party apps with account access.
3. Remove access for any legacy sync utilities, mail backup tools, or automation plugins that have read/write access to Gmail.

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Step 3: Limit IMAP Exposure in Gmail Settings

Once your access is restored, modify your Gmail settings to prevent future bandwidth exhaustion:

1. In Gmail, click the Gear icon and select See all settings.
2. Go to the Labels tab.
3. Locate All Mail and Trash under System labels, and uncheck “Show in IMAP”. This prevents clients from downloading duplicates of every message in your account.
4. Switch to the Forwarding and POP/IMAP tab.
5. Under Folder size limits, select “Limit IMAP folders to contain no more than this many messages” and set the limit to 1,000 or 2,000.
6. Save your changes.

For a deeper dive into optimizing message caps, see How to Increase IMAP Folder Limits.

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Step 4: Stagger Large-Scale Mailbox Migrations

If you are intentionally uploading or downloading large volumes of mail as part of an offboarding or onboarding process, avoid doing so over standard consumer IMAP. Use specialized enterprise migration tools that handle API rate-limiting gracefully, as detailed in Fix: “Migration failed for user: 403 Rate Limit”.