Should I resend emails to users with soft bounces due to full mailboxes, and what bounce rate is acceptable?
Matthew Whittaker
Co-founder & CTO, Suped
Published 17 May 2025
Updated 17 Aug 2025
7 min read
Dealing with email bounces is a common challenge for anyone sending emails. Specifically, soft bounces due to full mailboxes can be particularly perplexing. On one hand, you want to ensure your messages reach active subscribers, but on the other, you are concerned about maintaining a healthy sender reputation.
The question of whether to resend to these users, or when to simply suppress them, often arises. It is a balancing act between re-engagement efforts and safeguarding your email deliverability. I frequently see questions about this from email marketers who are trying to optimize their campaigns without inadvertently harming their sender score.
In this discussion, I will explore the nuances of soft bounces, specifically those caused by full mailboxes. I will also provide guidance on whether to resend and what constitutes an acceptable bounce rate for your email programs. Understanding these factors is crucial for successful email delivery.
Understanding soft bounces
Before diving into resending strategies, it is important to understand what a soft bounce is and how it differs from a hard bounce. A soft bounce indicates a temporary delivery issue, meaning the email address is valid but the message could not be delivered at that specific moment. This is in contrast to a hard bounce, which signifies a permanent delivery failure, often due to an invalid or non-existent email address. You can learn more about how soft bounces differ from hard bounces through additional resources on bounces.
A common reason for a soft bounce is a full mailbox or out of storage. This means the recipient's inbox has reached its capacity, and no new emails can be received until space is freed up. Other temporary issues causing soft bounces include the recipient's server being temporarily down or overloaded, or the email message size being too large.
The temporary nature of soft bounces suggests that a retry could be successful. However, repeatedly sending to addresses that consistently soft bounce, even for full mailboxes, can negatively affect your sender reputation and lead to your emails being flagged as spam. This is why careful management is essential.
Soft bounces versus hard bounces
Soft bounce: Temporary delivery failure due to issues like a full mailbox, server downtime, or large message size. The email address is valid.
Hard bounce: Permanent delivery failure, indicating the email address is invalid, nonexistent, or has been permanently blocked. Always remove these from your list.
Should you resend emails to full mailboxes?
The primary question is whether to resend emails to users who soft-bounced because their mailbox was full. In general, it is acceptable to retry sending to soft-bounced addresses. The assumption is that the issue is temporary, and the recipient might clear their inbox soon. However, this strategy requires careful consideration.
If you continue to send emails to an address that consistently soft bounces (or blocklists) due to a full mailbox, it can be detrimental. Internet Service Providers (ISPs) and mailbox providers like Gmail view repeated soft bounces as a sign of a neglected or inactive list. This can lead to lower sender scores and impact your overall email deliverability and sender reputation, increasing the likelihood of future emails landing in the spam folder.
Therefore, while a single soft bounce from a full mailbox can often be safely retried, a pattern of continuous soft bounces (even for the same reason) suggests you should consider suppressing the address. Sending to accounts that are consistently full is a red flag for mailbox providers. It is generally not advisable to keep sending to addresses that keep soft bouncing, as discussed in this article about bad email practices.
Considerations for resending
Temporary nature: Mailbox full is often a temporary state. The recipient might clear their inbox.
User engagement: If the user shows other signs of engagement (e.g., website activity, recent opens), it might be worth a retry.
Valuable content: For critical transactional emails, a retry is often necessary.
Risks of continuous resending
Sender reputation: ISPs monitor repeated bounces. High bounce rates harm your sender score.
Resource waste: You expend resources sending emails that likely will not be delivered.
Managing soft bounces and mailbox full issues
Managing soft bounces effectively is key to maintaining good email deliverability. While a few soft bounces are normal, a high volume of them, especially for the same recipients, requires action. You should implement a robust suppression logic within your email platform. This involves tracking bounce types and reasons.
For mailbox full bounces, many email service providers automatically retry sending for a period, typically 24-72 hours. If the email continues to soft bounce after multiple retries, it is generally recommended to suppress that address from future sends for a period or indefinitely. The exact number of retries and suppression period can vary, but a common practice is to suppress after 3-5 consecutive soft bounces over a short timeframe. Read more about recommended soft bounce suppression logic.
Beyond automated suppression, regularly cleaning your email lists is a fundamental best practice. This means removing unengaged subscribers and those who consistently soft bounce. A clean list ensures you are sending to an active audience, which positively impacts your domain reputation and overall deliverability. For more on this, check out our guide on cleaning soft bounces in email marketing.
Best practices for managing mailbox full bounces
Automated retries: Allow your sending platform to handle initial retries for soft bounces.
Implement suppression: Suppress addresses that soft bounce consistently (e.g., 3-5 times) within a defined period.
Monitor engagement: Combine bounce data with engagement metrics to make informed suppression decisions.
Segment lists: Separate highly engaged users from less engaged ones to tailor sending strategies.
What is an acceptable bounce rate?
A crucial aspect of email deliverability is understanding and managing your overall email bounce rate. The bounce rate is simply the percentage of emails that could not be delivered to the recipient's inbox. It is calculated by dividing the number of bounced emails by the number of emails sent. You want to keep this number as low as possible.
For general email marketing, a bounce rate below 2% is widely considered healthy and acceptable. Some sources even suggest aiming for below 1%. While a 0% bounce rate is almost impossible to achieve, striving for the lowest possible rate is always the goal. For more detailed benchmarks on acceptable rates, especially concerning soft and hard bounces, refer to our comprehensive guide on bounce rates.
High bounce rates, particularly hard bounces, signal to ISPs that your list quality is poor or that you may be sending unsolicited mail. This can lead to your IP address or domain being added to a blocklist (or blacklist), severely impacting your deliverability. Even consistent soft bounces, if not managed, can contribute to a declining sender reputation, leading to lower inbox placement rates. For further reading, an article on understanding soft and hard bounces provides additional insights.
Bounce type
Acceptable rate
Overall bounce rate
Below 2% is ideal
Hard bounce rate
As close to 0% as possible, ideally below 0.5%
Soft bounce rate
Typically tolerated up to 2-5%, but lower is always better.
Views from the trenches
Best practices
Implement an automated soft bounce suppression policy after a few retries.
Segment your audience by engagement to prioritize sending to active users.
Regularly clean your email lists to remove unengaged subscribers and frequent bouncers.
Monitor your bounce rates closely and identify any trending issues.
Tailor sending frequency to user engagement levels.
Common pitfalls
Continuously sending to addresses that consistently soft bounce due to full mailboxes.
Not having a clear suppression policy for repeated soft bounces.
Ignoring soft bounces, assuming they will always resolve on their own.
Failing to segment lists, leading to over-mailing unengaged or problematic addresses.
Over-focusing on daily bounce rates without considering long-term patterns.
Expert tips
For Gmail users, consider that their storage limits include photos and other data, not just email, so a full mailbox can be temporary.
A 0.1% bounce rate for a specific mailbox provider is extremely low and generally not a concern.
Automated segmentation towards engaged cohorts can effectively manage full mailboxes and general disinterest.
Your existing sunset policy for lack of engagement (e.g., no opens/clicks for 6-12 months) is a good blanket policy.
Sending frequency heavily influences deliverability; more frequent sending requires very high engagement.
Marketer view
Marketer from Email Geeks says they have seen users with full mailboxes return quite a bit, and they have not observed any negative impact from continuing to mail them without suppression.
2024-01-26 - Email Geeks
Expert view
Expert from Email Geeks says the usefulness of bounce count depends on the time period between bounces, for example, three bounces in one day might resolve, but three over three months suggests permanent disengagement. They advise reviewing historical data.
2024-01-26 - Email Geeks
Striking the right balance
Navigating soft bounces, particularly those from full mailboxes, requires a balanced and data-driven approach. While the initial instinct might be to resend, consistent bounces demand a more cautious strategy to protect your sender reputation. It is about understanding the temporary nature of these issues versus the long-term impact of perceived poor sending practices.
Gmail view repeated soft bounces as a sign of a neglected or inactive list. This can lead to lower sender scores and impact your overall email deliverability and sender reputation, increasing the likelihood of future emails landing in the spam folder.
