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Summary

Managing Gmail addresses with overquota inboxes is a common challenge for email marketers. These 'mailbox full' bounces are typically classified as soft bounces, indicating a temporary issue rather than a permanent invalid address. However, repeatedly sending to these addresses can impact sender reputation and overall deliverability. The key is to determine an appropriate suppression strategy that balances maintaining list hygiene with retaining potentially engaged subscribers who might clear their inbox space.

What email marketers say

Email marketers often approach overquota Gmail inboxes with a pragmatic view, recognizing that while these are soft bounces, they frequently indicate disengaged or unmonitored accounts. The general sentiment leans towards implementing a suppression strategy after a certain number of consecutive bounces, rather than persistently sending to addresses that consistently return an overquota error. There's a balance to strike between preserving potential long-term engagement and maintaining good sending hygiene.

Marketer view

Email marketer from Email Geeks suggests automatically opting out recipients after receiving 3-5 consecutive overquota bounces across distinct days. They find that, more often than not, these mailboxes are simply unmonitored.

07 Mar 2020 - Email Geeks

Marketer view

Email marketer from Email Geeks states that Gmail accounts generally have substantial storage, making it challenging to fill them under normal circumstances. Therefore, consistent overquota bounces often point to inactive accounts, which should be suppressed by most providers.

07 Mar 2020 - Email Geeks

What the experts say

Experts in email deliverability offer nuanced perspectives on overquota Gmail inboxes, often challenging common assumptions. While recognizing the importance of managing soft bounces for reputation, they highlight that a 'mailbox full' message doesn't always mean permanent inactivity. Research suggests a notable percentage of these addresses may become active again. The consensus emphasizes a data-driven approach to suppression policies, balancing the desire to retain subscribers with the need to maintain a healthy sending relationship with mailbox providers.

Expert view

Deliverability expert from Email Geeks shared research indicating that around one-third of all 'mailbox full' bounces actually resulted in an open within 12 months, suggesting these addresses aren't always permanently defunct.

07 Mar 2020 - Email Geeks

Expert view

A deliverability expert from Email Geeks emphasizes that it's often easier to retain an existing subscriber than to expect them to notice a missed email due to a full inbox and then go through the effort of resubscribing, especially if it requires contacting support.

07 Mar 2020 - Email Geeks

What the documentation says

Official email documentation, such as RFCs (Request for Comments), categorizes bounce messages to guide how mail servers should interpret and react to delivery failures. An 'overquota' or 'mailbox full' response is generally treated as a temporary failure. While the SMTP protocol indicates these are transient issues, continued delivery attempts to such addresses without a successful delivery can signal poor sending practices to receiving mail servers, potentially affecting sender reputation over time. Best practices emphasize respecting bounce codes and adapting sending behavior accordingly.

Technical article

RFC 5321 (SMTP) specifies that a 4XX response code indicates a transient negative completion reply. This means the message could not be delivered at this time, but the sender is encouraged to try again later.

01 Oct 2008 - RFC 5321

Technical article

Gmail Postmaster Tools documentation advises senders to monitor bounce rates. A high bounce rate, even from soft bounces like 'overquota', can be an indicator of poor list quality or sending practices, impacting sender reputation.

22 Jun 2023 - Gmail Postmaster Tools Help

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    How should email marketers handle Gmail addresses with overquota inboxes? - Sender reputation - Email deliverability - Knowledge base - Suped