Summary
Email marketers and documentation sources offer varied strategies for handling Gmail addresses with overquota inboxes, balancing deliverability and engagement. The primary recommendation involves bounce management: treat initial 'mailbox full' bounces as soft bounces, but implement suppression after a defined period (3-4 weeks, 3-5 bounces), acknowledging a segment may still engage later. Alternative tactics include segmenting full mailboxes for targeted re-engagement, creating 'can't miss' content, or adjusting soft bounce tolerance. Ensuring proper authentication (SPF, DKIM, DMARC) is paramount. Opinions are divided, some lean towards immediate suppression to protect sender reputation, while others favor limited reactivation efforts.
Key findings
- Bounce as Indicator: A 'mailbox full' bounce signifies a reached storage limit, signaling potential inactivity.
- Soft Bounce -> Hard Bounce: Initial treatment is soft bounce, conversion to hard bounce follows persistence.
- Suppression Key: Suppression after a defined period safeguards sender reputation and deliverability.
- Engagement Possibility: A percentage of users open emails within 12 months even after mailbox full errors.
- Segmentation Option: Segmenting full mailboxes supports re-engagement experimentation.
Key considerations
- Suppression Timeline: Determine optimal timeframe for suppression to balance hygiene and engagement.
- Content Value: Evaluate the resource investment for highly valuable content creation.
- Authentication Importance: Proper authentication is crucial for maintaining trust with Gmail.
- Soft Bounce Parameters: Adjust ESP soft bounce tolerances based on sending frequency.
- Reputation Impact: Continuously monitoring bounce volumes is crucial for the reputation.
What email marketers say
15 marketer opinions
Email marketers handle Gmail addresses with overquota inboxes through various strategies, primarily revolving around bounce management and maintaining sender reputation. These strategies include immediate suppression after a few bounces, implementing bounce management systems, segmenting and treating these addresses as inactive, and using soft bounce tolerances. Reactivation campaigns are sometimes recommended, but monitoring sender reputation and the potential for damaging it due to continued sending is a significant consideration. Recommendations include suppressing after 3-5 bounces across distinct days, waiting 3-4 weeks without a successful delivery, but also being wary that up to a third of these mailboxes may be opened within 12 months.
Key opinions
- Immediate Suppression: Some marketers opt-out addresses after a few consecutive bounces, viewing them as unmonitored.
- Bounce Management Systems: Implementing automated systems can streamline the suppression of persistently full mailboxes.
- Segmentation: Creating segments for 'over quota' addresses allows for targeted re-engagement attempts or experimentation with timing.
- Soft Bounce Tolerance: Adjusting the soft bounce tolerance in ESP settings can influence how quickly addresses are suppressed.
- Reactivation potential: Research show that as much as 30% of mailboxes are opened again so suppression may not be ideal.
Key considerations
- Sender Reputation: Continuing to send to full mailboxes can negatively impact sender reputation and deliverability.
- Authentication: Ensure proper email authentication (SPF, DKIM, DMARC) to maintain trust with Gmail.
- Re-engagement: Weigh the benefits of re-engagement campaigns against the risk of continued bounces.
- Suppression Timing: Determine an appropriate timeframe for suppression to balance list hygiene with potential lost contacts. Also taking into account any research on when mailboxes become active again.
- Soft vs Hard Bounce: Determine whether mailbox full errors are soft bounces and ensure correct suppression is enabled based on that categorization.
Marketer view
Marketer from Email Geeks shares research finding that around 1/3 of all Mailbox Full bounces opened another email within 12 months.
21 Dec 2021 - Email Geeks
Marketer view
Email marketer from Mailtrap Blog shares that a bounce management strategy is essential, particularly for 'mailbox full' errors. They suggest a grace period followed by suppression to avoid damaging sender reputation. Also to send a retry or resend after 24 hours to a full mailbox.
17 May 2025 - Mailtrap Blog
What the experts say
2 expert opinions
Experts offer contrasting views on handling full Gmail inboxes. One suggests that a full inbox indicates abandonment, warranting invalidation. Conversely, another proposes that users may retain emails with the intent of future reference, recommending the creation of highly valuable, 'can't miss' content to incentivize space-clearing and engagement.
Key opinions
- Abandonment Indication: A full Gmail inbox can signify an abandoned or inactive account.
- Value-Driven Engagement: High-value content may incentivize users to clear space in their inbox to receive the email.
Key considerations
- Action Strategy: Decide whether to suppress addresses deemed abandoned or attempt re-engagement with targeted content.
- Content Investment: Assess the resources required to create 'can't miss' content and its potential return.
- Inbox behavior: Decide whether a full mailbox means the user is not active or they may delete old emails to make room.
Expert view
Expert from Word to the Wise indicates that when people have full inboxes they are probably not deleting because they feel they may need the email at some point in time. Therefore, Laura Belgray recommends sending something of high value that would encourage them to delete another email to make space for yours. This needs to be a "can't miss" email.
3 Apr 2023 - Word to the Wise
Expert view
Expert from Email Geeks suggests that a full Gmail inbox is probably abandoned and multiple bounces over time would be a good reason to invalidate it.
10 Mar 2023 - Email Geeks
What the documentation says
5 technical articles
Technical documentation generally agrees that a 'mailbox full' bounce indicates the recipient's inbox has reached its limit. While initially treated as soft bounces, persistent occurrences suggest inactivity and warrant eventual suppression. Monitoring bounce notifications and setting up automated removal processes are key to maintaining list hygiene.
Key findings
- Mailbox Full = Limit Reached: A 'mailbox full' bounce confirms the recipient's inbox is at capacity.
- Soft Bounce Initial Treatment: These bounces are typically considered temporary failures initially.
- Persistent Bounces = Inactivity: Repeated 'mailbox full' errors strongly indicate the address is inactive or abandoned.
- Eventual Suppression: Inactive addresses should eventually be suppressed to maintain list quality.
- SMTP 552 Code: The SMTP error code 552 signals that the mailbox's storage allocation has been exceeded.
Key considerations
- Monitoring Bounce Notifications: Actively monitor bounce notifications to identify persistent 'mailbox full' errors.
- Automated Removal Processes: Implement automated systems to remove consistently bouncing addresses from sending lists.
- Soft to Hard Bounce Conversion: Define a specific threshold (attempts/timeframe) for converting soft bounces to hard bounces for suppression.
- Handling: These bounces should have a certain set of soft bounce attempts before converting to hard bounces.
Technical article
Documentation from Google Workspace Admin Help explains that a 'mailbox full' bounce indicates the recipient's inbox has reached its storage limit and cannot accept new messages. Persistent bounces suggest the address is inactive or abandoned.
15 Feb 2024 - Google Workspace Admin Help
Technical article
Documentation from SparkPost notes that 'mailbox full' errors are classified as soft bounces, but repeated occurrences indicate a more permanent issue and should be handled accordingly with the goal of suppression.
7 Oct 2022 - SparkPost
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