Why is there a sudden spike in Gmail 'mailbox full' bounces since August 2024?

Email marketer from Email Vendor Blog shares that the quota enforcement means marketers need to be more aggressive about suppressing inactive users or users who consistently bounce with mailbox full errors to protect sender reputation and ensure deliverability for engaged users.

Email marketer from Email Sender Forum recommends ensuring that all email authentication protocols (SPF, DKIM, DMARC) are correctly configured, as deliverability issues can sometimes manifest as increased bounces.

Email marketer from Reddit mentions that persistent mailbox full bounces are an indicator of unengaged users. He suggests implementing a re-engagement campaign before completely removing them from your mailing list.

Email marketer from Email on Acid Blog suggests monitoring Google Postmaster Tools for any changes in spam rate or domain reputation that may coincide with the spike in mailbox full bounces, as these can be contributing factors.

Email marketer from Reddit explains that possible causes could be users uploading more data (photos, documents) which is now contributing more to storage, Gmail's algorithm changes, or even users simply not managing their inboxes effectively. They also state it may be related to a new Google One promotion filling user storage

Email marketer from Email Marketing Tips Forum reports that some users have posted about Gmail altering the quota amount for Google One customers, or changes to how shared storage between services (Gmail, Drive, Photos) is calculated.

Email marketer from Litmus Community suggests verifying bounce message classifications with your ESP, as some systems may misclassify other deliverability issues as mailbox full bounces.

Email marketer from StackExchange shares a strategy of implementing temporary suppression for users who receive mailbox full errors, retry sending after a few days, and then permanently suppress if the issue persists to maintain sender reputation.

Email marketer from Email Deliverability Blog suggests creating a segment specifically for recipients who return 'mailbox full' bounces. Monitor this segment closely and suppress those users after a certain number of bounces within a defined period.

Marketer from Email Geeks shares that they are seeing the same 'mailbox full' bounce error, starting around the same time. They also state that they use a temporary suppression strategy for over quota errors, retrying a few days later and fully suppressing if the issue persists.

Email marketer from Google Support Forum explains that the bounce spike is likely due to Google enforcing storage limits more strictly. Before August 2024, Gmail allowed users to exceed their storage quota and still receive emails. Now, Gmail bounces emails immediately when a user is over quota, leading to a sudden increase in 'mailbox full' errors.

Marketer from Email Geeks shares that their ESP (Iterable) contacted Google and discovered that the recent increase in quota errors is due to Google's updated policy on handling users who are out of quota. Previously, Gmail allowed such inboxes to accept messages despite being over quota, but starting around August 15th, Google began strictly enforcing these limits, leading to a spike in `MailboxFull` errors. The marketer's contact anticipates that this initial spike will decrease as users remove or suppress these users or reduce the frequency of emails sent to them and advises implementing suppression rules for these soft bounces.

Expert from Word to the Wise explains that bounce management is crucial for maintaining a good sending reputation. They delve into how to handle both hard and soft bounces effectively, highlighting the importance of correctly interpreting bounce codes and promptly removing problematic addresses from mailing lists, although it does not specify to the increase in bounces in August 2024.

Expert from Email Geeks explains that the rejection message containing '[internal] message timeout' indicates a deferral translated into a hard bounce by the ESP. The expert further suggests that the core question is why a large number of recipients ran out of space over the weekend.

Expert from Email Geeks explains that because the deferrals are escalated to hard bounces, the issue (deferrals) will have started some time before the chart started going up. The expert suggests that if something different was done, say, on the 13th, that might be relevant. They also mention the deferral issue has been gradually increasing for a while.

Expert from Spam Resource explains that 'mailbox full' bounces should be treated as a signal. It suggests a strategy of immediate temporary suppression followed by permanent suppression after several failed retry attempts to protect sender reputation. They don't specifically address the August 2024 spike, but provide guidance on how to manage 'mailbox full' bounces in general.

Documentation from Mailjet explains that mailbox full errors are considered soft bounces. It suggests following best practices such as throttling email volume and allowing ample time for Gmail to retry delivery before classifying the bounce as permanent.

Documentation from Google Developers defines 452 4.2.2 as 'The recipient's mailbox is out of storage space' and 552 4.2.2 'The email account that you tried to reach is over quota'. This confirms that the bounce messages are legitimate.

Documentation from SparkPost explains that a 'mailbox full' bounce is often a soft bounce, but if it persists over time, the user likely isn't actively managing their account. It also explains that stricter enforcement of mailbox quotas can lead to sudden spikes in these bounces.

Documentation from Google Workspace Admin Help states that each Google Account comes with 15 GB of storage that is shared across Google Drive, Gmail, and Google Photos. Google may be enforcing these limits more effectively, resulting in bounces.