Summary
Mailbox disabled bounces are generally considered soft bounces, but can indicate a variety of issues. While sometimes temporary, they often represent bad or inactive addresses. Major mailbox providers might return this bounce code even for valid addresses, but repeated sending negatively impacts sender reputation, increasing the risk of being flagged as spam. Experts recommend promptly removing these addresses and practicing good list hygiene. A surge in such bounces signals underlying list problems. While often not a spam trap, failing to address them harms your deliverability.
Key findings
- Reputation Impact: High bounce rates, especially from 'mailbox disabled' bounces, negatively impact sender reputation and can lead to being flagged as spam.
- List Hygiene Importance: Maintaining a clean email list by regularly removing invalid or inactive addresses is essential for deliverability.
- Soft Bounce Caveat: While technically soft bounces, 'mailbox disabled' bounces often signify permanent problems and should not be ignored.
- Not Always Spam: Though not always spam traps, repeatedly sending to 'mailbox disabled' addresses increases the chances of deliverability issues.
- Root Cause Analysis: A sudden increase in 'mailbox disabled' bounces points to underlying problems with data acquisition or list maintenance practices.
Key considerations
- Prompt Removal: Promptly remove 'mailbox disabled' addresses from your list to protect your sender reputation.
- Avoid Repeated Sending: Pause sending to 'mailbox disabled' addresses temporarily or suppress them to prevent further deliverability issues.
- Monitor Metrics: Closely monitor bounce rates and investigate increases in 'mailbox disabled' bounces.
- Validate Email Lists: Use email validation services to proactively identify and remove invalid or inactive addresses.
- Improve Acquisition: Review and improve email acquisition practices to ensure the collection of valid and engaged email addresses.
What email marketers say
14 marketer opinions
Mailbox disabled bounces can indicate several issues impacting email deliverability. While conceptually soft bounces, they often represent bad addresses. Major mailbox providers may return this for valid addresses that will become invalid. Repeated sending hurts sender reputation, risking spam flags. List validation services help identify and remove these addresses. Best practice involves suppressing these addresses, pausing sends, and practicing good email hygiene by regularly cleaning lists. While not always a spam trap, persistently sending to such addresses can negatively affect your reputation with ISPs.
Key opinions
- Impact on Reputation: High bounce rates, including 'mailbox disabled' bounces, negatively impact sender reputation, signaling questionable email practices to ISPs.
- List Hygiene: Regularly cleaning email lists and removing invalid addresses, including disabled mailboxes, is crucial for maintaining good deliverability.
- Soft vs. Hard Bounce: While conceptually soft bounces, 'mailbox disabled' bounces can turn into hard bounces and should be treated seriously.
- Not Always Spam Traps: Although not always indicative of spam traps, sending to 'mailbox disabled' addresses increases the risk of being flagged as spam.
- Validation Importance: Using list validation services helps identify and remove invalid addresses, preventing 'mailbox disabled' bounces.
Key considerations
- Suppress Bounces: Suppress 'mailbox disabled' bounces from future sends to improve sender reputation.
- Pause Sending: Pause sending to addresses that result in 'mailbox disabled' bounces temporarily to avoid deliverability problems.
- Monitor Metrics: Closely monitor email marketing metrics, including bounce rates, to identify potential issues with list hygiene.
- Use Validation Services: Employ email list validation services to proactively identify and remove invalid addresses.
- Address as Bad: Treat mailbox disabled bounces as potentially bad addresses and remove them to minimise harm.
Marketer view
Email marketer from Email on Acid notes that a 'mailbox disabled' bounce typically indicates that the recipient's email account is no longer active. Continuing to send to these addresses signals to mailbox providers that you’re not maintaining your list, potentially hurting your sender reputation.
29 Aug 2021 - Email on Acid
Marketer view
Email marketer from Mailjet's blog advises regularly cleaning email lists to remove invalid or inactive addresses. They emphasize that sending to 'mailbox disabled' addresses repeatedly not only wastes resources but also harms sender reputation and increases the likelihood of being flagged as spam.
23 Aug 2022 - Mailjet
What the experts say
2 expert opinions
Experts emphasize that properly handling mailbox disabled bounces is crucial for maintaining good deliverability. These bounces indicate potentially invalid addresses, and promptly removing them from your list improves sender reputation and reduces the risk of being flagged as a spammer. A sudden increase in hard bounces, including mailbox disabled errors after repeated attempts, signals underlying problems with your email list, such as stale data or poor acquisition practices.
Key opinions
- Bounce Handling Critical: Properly handling bounces, particularly mailbox disabled bounces, is essential for maintaining good email deliverability.
- Indication of Invalid Addresses: Mailbox disabled bounces serve as indicators of potentially invalid email addresses.
- Impact on Sender Reputation: Failing to address mailbox disabled bounces can negatively impact your sender reputation, increasing the risk of being flagged as a spammer.
- Sign of Underlying Problems: A sudden spike in hard bounces, including mailbox disabled errors, suggests underlying problems with your email list, such as stale data.
Key considerations
- Prompt Removal: Remove mailbox disabled email addresses from your list promptly to improve sender reputation.
- Investigate Bounce Spikes: Investigate the cause of sudden spikes in hard bounces, including mailbox disabled errors, to identify and rectify underlying issues with your email list.
- Review Acquisition Practices: Review your email acquisition practices to ensure you are not inadvertently collecting invalid email addresses.
Expert view
Expert from Word to the Wise (Laura Atkins) explains that a sudden increase in hard bounces, which can include 'mailbox disabled' errors after repeated attempts, indicates underlying problems with your email list, such as stale data or acquisition practices leading to invalid addresses. This increases your risk of being flagged as a spammer.
30 Jun 2022 - Word to the Wise
Expert view
Expert from Spam Resource explains that properly handling bounces is critical for maintaining good deliverability. Treating 'mailbox disabled' bounces as indicators of potentially invalid addresses and removing them from your list promptly will improve your sender reputation and prevent being seen as a spammer.
15 Nov 2022 - Spam Resource
What the documentation says
4 technical articles
Documentation indicates that 'mailbox disabled' bounces can arise from various reasons, including the recipient's address not existing (Microsoft), the user's account being suspended, the mailbox being full, or the domain no longer existing (SendGrid). Though generally considered soft bounces (SparkPost), repeated soft bounces can be treated as hard bounces, negatively impacting deliverability. Sending to these addresses repeatedly can hurt your sender reputation with ISPs (Microsoft, SendGrid) and may even contribute to spam scores if the address is a spam trap (RFC Editor).
Key findings
- Recipient Address Issue: 'Mailbox disabled' bounces often indicate an issue with the recipient's email address.
- Soft vs. Hard Bounce: Although typically considered soft bounces, repeated bounces can be treated as hard bounces with negative consequences.
- Sender Reputation: Repeatedly sending to 'mailbox disabled' addresses damages your sender reputation with ISPs.
- Potential Spam Traps: Mailbox disabled bounces can potentially indicate spam traps if the address was once valid.
Key considerations
- Monitor and Remove: Regularly monitor and remove 'mailbox disabled' email addresses from your sending list.
- Handle Appropriately: Handle soft bounces carefully, avoiding repeated sending to the same address.
- Review List Hygiene: Review email list hygiene practices to prevent sending to invalid or disabled mailboxes.
Technical article
Documentation from SparkPost explains the difference between hard and soft bounces. A 'mailbox disabled' bounce is generally considered a soft bounce, indicating a temporary issue. However, repeated soft bounces to the same address can be treated as a hard bounce, signaling a permanent problem with the address and negatively impacting deliverability.
19 Jun 2023 - SparkPost
Technical article
Documentation from SendGrid explains that 'mailbox disabled' bounces can arise from various reasons, including the user's account being suspended, the mailbox being full, or the domain no longer existing. Continually sending to these addresses will hurt your sender reputation with ISPs.
15 May 2025 - SendGrid
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