Why does a Gmail address report being over quota and then start receiving mail again?

When a Gmail account reaches its storage limit, incoming emails are temporarily blocked, resulting in bounce messages indicating 'over quota' or 'mailbox full'. However, users can quickly free up space by deleting large files from Google Drive, purging old photos from Google Photos, or emptying their Gmail trash and spam folders. Alternatively, they might opt to purchase additional storage from Google One, instantly resolving the quota issue and allowing mail delivery to resume. Senders often observe this temporary state because many mail servers are configured to retry sending for a period, typically up to 48-72 hours, allowing time for the recipient to clear space or expand their storage.

Key findings

• Shared storage: Gmail's 15GB storage quota is shared across Gmail, Google Drive, and Google Photos. This means non-email files can quickly fill up the available space.
• Temporary bounce: When over quota, incoming emails receive a soft bounce, typically an SMTP 4.2.2 error. Sending mail servers will usually retry delivery for a defined period.
• User action: Users can manually delete large files from Drive or Photos, empty trash, or purchase more storage to resolve the issue quickly.
• Automatic resumption: Once space is freed or expanded, subsequent delivery attempts from the sender's mail server will succeed, making it appear as if the address started receiving mail again after a brief interruption.
• Deliverability impact: Consistent bounces due to over-quota mailboxes, even if temporary, can negatively affect sender reputation if not managed properly. This can lead to delivery delays or even future rejections.

Key considerations

• Bounce handling: Implement robust bounce management. While temporary, repeated over-quota bounces for an address over a short period might indicate an inactive or poorly managed account that could eventually become a hard bounce.
• User education: If you manage Google Workspace accounts, educate users about shared storage and how to manage it effectively to prevent delivery interruptions.
• Retry logic: Understand your email service provider's (ESP) retry policy for soft bounces. Most will retry for at least 24-72 hours, which is typically sufficient for users to clear space or upgrade.
• Monitoring: Keep an eye on your bounce rates for Gmail recipients to detect any abnormal spikes that might indicate widespread recipient storage issues or other deliverability problems.

Understanding this behavior is important for marketers because it directly impacts email deliverability and list hygiene. Properly handling soft bounces from over-quota messages ensures that you avoid unnecessarily penalizing legitimate, engaged subscribers who might simply be experiencing a temporary storage crunch. It also informs how you segment your lists and manage re-engagement campaigns.

Key opinions

• It happens: Many marketers confirm they have seen Gmail addresses go over quota briefly and then become deliverable again, indicating it's not an unusual occurrence.
• Shared Google space: The shared 15GB across Gmail, Google Drive, and Google Photos is a primary reason for temporary over-quota issues, as large files unrelated to email can consume space rapidly.
• User action and payment: Users often clear space by deleting old files (like photos from Android devices) or by purchasing additional Google One storage, which immediately resolves the quota problem.
• Impact on marketing: Marketers should treat 'over quota' as a soft bounce and retry sending, as the issue is often temporary. This helps maintain list quality without prematurely removing active subscribers.

Key considerations

• Segment bounces: Differentiate between soft bounces (like over quota) and hard bounces in your email reports. Soft bounces warrant retries, while hard bounces require immediate removal.
• List hygiene practices: While over-quota messages are temporary, consistent bounces from an address over a longer period (e.g., several weeks) might indicate a truly abandoned or inactive account that should be suppressed.
• Sender reputation: Excessive soft bounces, even if temporary, can reflect poorly on your sender reputation. Keep your bounce rates low by identifying and managing problematic addresses efficiently.
• Content and file size: Consider if your email content itself, or attachments within your emails (if any), are contributing to recipient mailbox fullness, especially for transactional emails with large files.

They highlight the importance of proper bounce management and list hygiene, especially when dealing with temporary delivery failures. Ignoring these temporary blocks can lead to increased bounce rates, which may negatively impact sender reputation over time. Experts also advise monitoring Google Postmaster Tools for insights into Gmail delivery, as it can provide broader trends in bounce rates.

Key opinions

• Normal behavior: Experts confirm that Gmail accounts temporarily exceeding their quota and then recovering is a routine occurrence, not an anomaly.
• Storage management: The ability of users to quickly delete large files from Google Drive or Google Photos, or upgrade their storage plan, means the over-quota state is often short-lived.
• Soft bounce differentiation: It is crucial to categorize 'over quota' as a soft bounce, prompting retries rather than immediate suppression, to avoid losing active subscribers.
• Retry window: Sending mail servers typically retry delivery for a period (e.g., 24-72 hours), allowing time for the recipient to clear space or purchase more storage.

Key considerations

• Automated bounce processing: Ensure your ESP or sending system is configured to properly manage soft bounces, distinguishing them from permanent failures and implementing appropriate retry logic.
• Monitoring bounce rates: Continuously monitor your bounce rates, especially for Gmail, to identify if over-quota bounces become a persistent issue for certain addresses or a wider trend, which could signal a list quality problem.
• List hygiene automation: While retries are good, establish rules for when repeated soft bounces (e.g., after a week of consistent over-quota messages) should lead to temporary suppression or removal to protect sender reputation.
• Understanding SMTP codes: Familiarize yourself with SMTP bounce codes, particularly 4xx series (temporary failures) versus 5xx series (permanent failures), to accurately diagnose delivery issues. Proton's SMTP error documentation provides good insight.

Understanding these documented policies is crucial for compliance and optimizing email deliverability. Mailbox providers, including Gmail, implement specific policies to prevent spam and ensure service stability, which includes managing storage quotas. Senders are expected to adhere to Gmail's sending policies and guidelines, which implicitly cover how 'over quota' situations are handled.

Key findings

• Integrated storage: Gmail's storage quota is integrated with Google Drive and Google Photos, meaning any data stored across these services counts towards the total 15GB free limit.
• Quota enforcement: Exceeding the storage quota leads to a prohibition on sending or receiving messages, as stated in Google's policies.
• SMTP 4xx errors: 'Over quota' messages typically result in a 4xx series SMTP error, like 4.2.2, which signifies a temporary failure and prompts the sending server to retry delivery.
• Retry behavior: Standard email protocols dictate that sending mail servers will attempt to resend messages that encounter temporary delivery failures for a specified period.

Key considerations

• User responsibility: Users are responsible for managing their storage to ensure continuous email reception. Gmail provides tools for users to check and clear their space.
• Automated deletion policies: Some services, including Google, may delete content from an account if storage quotas are consistently exceeded or if the account remains inactive, although this is usually for prolonged periods.
• Sender compliance: Senders should be aware of recipient mailbox policies to optimize their sending practices and avoid repeated, futile delivery attempts.
• Quota monitoring: For Google Workspace admins, it's possible to monitor storage usage for domains, providing proactive insights into potential quota issues for users.