How can I resolve high bounce rates and 'mailbox unavailable' errors for a specific domain?

Summary

To resolve high bounce rates and 'mailbox unavailable' errors for a specific domain, experts and documentation recommend a multi-faceted approach centered on diligent list hygiene. The foundational step involves promptly ceasing mailings to problematic addresses and removing invalid email addresses identified by 'mailbox unavailable' errors, as these indicate non-existent recipients. Email verification tools are essential for validating addresses, and regular list cleaning is crucial. Employing double opt-in and preference centers helps prevent future bounces. If bounces are domain-specific, contacting the IT department of that domain is advised. Standardized bounce messages and codes should be analyzed for insights. Aim for a bounce rate below 2%. Re-engagement campaigns can salvage potentially valid addresses, but a risk-benefit analysis is critical before continuing mailings to questionable addresses, considering the impact on sender reputation and deliverability.

Key findings

  • Mailbox Unavailable = Non-Existent: A 'mailbox unavailable' error typically signifies that the recipient's email address does not exist.
  • Immediate Removal of Hard Bounces: Hard bounces should be removed from your mailing list immediately to maintain sender reputation.
  • List Hygiene is Crucial: Regularly cleaning and validating your email list is fundamental for minimizing bounces.
  • Domain-Specific Issues Require Direct Contact: If bounces are concentrated on a specific domain, contact their IT department to resolve potential blocking issues.
  • Double Opt-In Prevents Invalid Addresses: Implementing double opt-in helps to ensure that only valid email addresses are added to your list.
  • Aim for <2% Bounce Rate: Strive to maintain a bounce rate of less than 2% for optimal email deliverability.

Key considerations

  • Sender Reputation at Risk: High bounce rates negatively impact sender reputation, potentially leading to deliverability problems.
  • Balance Revenue vs. Deliverability: Weigh the potential revenue from questionable email addresses against the risk to overall deliverability.
  • Analyze Bounce Messages and Codes: Carefully examine bounce messages and codes to diagnose the underlying causes of delivery failures.
  • Re-Engagement Campaigns: Consider using re-engagement campaigns to verify potentially valid addresses before removing them.
  • Impact of Old vs. New Lists: Bounces might be due to an old list.

What email marketers say
8Marketer opinions

To resolve high bounce rates and 'mailbox unavailable' errors for a specific domain, email marketers recommend focusing on list hygiene through regular cleaning, validation of email addresses before sending, and immediate removal of hard bounces. Implementing double opt-in and preference centers helps prevent bounces. Addressing domain-specific issues involves contacting the IT department of the affected domain to resolve any blocks. Aim for a bounce rate below 2% and engage email verification tools to ensure valid email addresses. Soft bounces should be monitored but not immediately removed.

Key opinions

  • List Hygiene: Regularly clean your email list by removing invalid addresses and inactive subscribers.
  • Double Opt-In: Use double opt-in to ensure subscribers have explicitly given permission to receive emails.
  • Hard Bounce Removal: Immediately remove hard bounces from your list to maintain a good sender reputation.
  • Domain Contact: Contact the IT department of the problematic domain to resolve blocks.
  • Verification Tools: Utilize email verification tools to confirm the validity of email addresses.
  • Good Bounce Rate: Aim for a bounce rate of below 2% to ensure good deliverability.

Key considerations

  • Sender Reputation: High bounce rates negatively impact sender reputation, affecting overall deliverability.
  • Email Validation: Validating email addresses helps prevent sending to invalid or non-existent mailboxes.
  • Soft vs. Hard Bounces: Differentiate between soft and hard bounces; soft bounces may resolve themselves, while hard bounces require immediate action.
  • Re-engagement: Consider sending re-engagement emails to confirm subscriber interest before removing them.
  • Specific Domain Issues: If issues are isolated to one domain, direct communication with their IT department is crucial.
  • Preference Center: Consider implementing a preference center to allow subscribers to manage their communication preferences.
Marketer view

Email marketer from Reddit User u/EmailExpert responds to a question of what to do with hard bounces. They recommend immediately removing hard bounces as keeping them on your list indicates you are not keeping your list clean which will result in a worse reputation with the IPs. They further suggest sending a re-engagement email to confirm whether they still wish to be engaged.

February 2022 - Reddit
Marketer view

Email marketer from Reddit User u/DeliverabilityGuru responds to a question of what to do with soft bounces. They suggest a soft bounce is a temporary issue and typically resolves itself. They advise waiting a few days before removing an email from your email list.

January 2022 - Reddit
Marketer view

Email marketer from Sendinblue shares that high bounce rates negatively impact sender reputation. They recommend segmenting your email list, cleaning your list regularly, and using double opt-in to ensure valid email addresses.

November 2022 - Sendinblue
Marketer view

Email marketer from Litmus shares that you can prevent bounces by obtaining explicit permission from subscribers (double opt-in) and implementing a preference center to allow subscribers to manage their communication preferences.

December 2022 - Litmus
Marketer view

Email marketer from ActiveCampaign shares what is a good bounce rate by saying you should be aiming for less than 2% and it's extremely important to regularly clean your email lists.

June 2022 - ActiveCampaign
Marketer view

Email marketer from EmailToolTester shares that you should use an email verification tool such as ZeroBounce or Neverbounce to ensure you are only sending email to real email addresses.

May 2022 - EmailToolTester
Marketer view

Email marketer from Mailjet shares that to improve email deliverability and reduce bounce rates, focusing on list hygiene is important. They recommend validating email addresses before sending and removing inactive subscribers.

June 2021 - Mailjet
Marketer view

Email marketer from HubSpot shares that if bounces are occurring specifically for one domain, you need to contact the IT department of that domain and ask them to unblock you. You should find out why you are blocked and remediate this.

July 2021 - HubSpot

What the experts say
7Expert opinions

Experts recommend addressing high bounce rates and 'mailbox unavailable' errors for a specific domain by first identifying the cause, which often points to a bad or outdated email list. The advice is to cease mailing to those addresses, verify domain existence through DNS checks, and remove unresponsive recipients. Investigating bounce messages, reviewing sending practices, and potentially contacting the domain's postmaster are also recommended. A key consideration is balancing potential revenue loss from removing addresses against the risk to overall deliverability and sender reputation.

Key opinions

  • Mailbox Unavailable: 'Mailbox unavailable' likely means the address no longer exists.
  • Stop Mailing: Cease sending emails to problematic addresses immediately.
  • Bad List: High bounce rates often indicate a poorly maintained or outdated email list.
  • DNS Check: Verify the domain still resolves in DNS.
  • Contact Postmaster: Attempt to contact the domain's postmaster for assistance.

Key considerations

  • Deliverability Risk: Weigh the risk to deliverability against the potential revenue from questionable addresses.
  • Lost Subscribers: Recognize that subscribers on the problematic list may already be lost.
  • Bounce Message Analysis: Carefully analyze bounce messages for clues about the cause of the failures.
  • Sending Practices: Review current sending practices for potential issues contributing to the problem.
  • Revenue Data: If available, get data on lost revenue attributed to unsubscribed emails.
Expert view

Expert from Word to the Wise explains that if a domain is completely unresponsive and bouncing all mail, it could indicate the domain no longer exists. They advise checking if the domain resolves in DNS and if not, removing all recipients with that domain from your mailing lists.

December 2021 - Word to the Wise
Expert view

Expert from Email Geeks explains that a 'mailbox unavailable' error means the email address no longer exists and suggests that the client tried to bring over their bounces.

August 2022 - Email Geeks
Expert view

Expert from Email Geeks suggests that the issue smells like a bad list and recommends focusing on that angle first. If the addresses are legitimate, suggests reaching out to Mail.com.

December 2024 - Email Geeks
Expert view

Expert from Email Geeks asks if the client wants to risk their deliverability and revenue from valid email addresses for the invalid addresses and whether the old platform showed revenue from the emails attributed to those subscribers.

October 2022 - Email Geeks
Expert view

Expert from Email Geeks explains that they may have already lost those subscribers and the zero revenue they represent.

August 2022 - Email Geeks
Expert view

Expert from Email Geeks suggests stopping mailing to the problematic addresses.

September 2024 - Email Geeks
Expert view

Expert from Word to the Wise explains that when facing deliverability issues with a specific domain, investigate bounce messages, review sending practices, and consider contacting the domain's postmaster. If the issue persists, it may indicate a broader deliverability problem requiring further investigation.

September 2024 - Word to the Wise

What the documentation says
5Technical articles

Documentation consistently advises that to resolve high bounce rates and 'mailbox unavailable' errors, the primary action is to remove invalid email addresses from your contact list. 'Mailbox unavailable' errors signify permanent delivery failures and require immediate removal of those addresses to protect sender reputation. Standardized bounce messages and bounce codes provide detailed information for diagnosing the causes of delivery failures, facilitating automated processing and accurate identification of issues.

Key findings

  • Remove Invalid Addresses: Eliminating invalid email addresses is crucial for reducing bounce rates.
  • Mailbox Unavailable = Permanent Failure: 'Mailbox unavailable' errors indicate a permanent delivery failure.
  • Immediate Hard Bounce Removal: Addresses causing hard bounces should be removed immediately.
  • Bounce Message Information: Standardized bounce messages offer machine-readable details about delivery failures.
  • Bounce Codes: Bounce codes provide specific information to help diagnose deliverability issues.

Key considerations

  • Sender Reputation Impact: High bounce rates harm sender reputation, so it's vital to maintain a clean list.
  • Automated Processing: Leverage automated systems to process bounce messages for efficient list management.
  • Diagnostic Importance: Understanding bounce codes is essential for diagnosing and addressing underlying issues with email delivery.
  • Data Driven Decisions: Make data driven decisions, remove recipients if the issue persists after verification.
Technical article

Documentation from Google Workspace Admin Help explains that to reduce bounce rates, you should remove invalid email addresses from your contact list. They recommend regularly cleaning your list by removing unsubscribed users and correcting typos.

July 2022 - Google Workspace Admin Help
Technical article

Documentation from SparkPost explains that 'mailbox unavailable' errors (hard bounces) indicate a permanent delivery failure. They advise immediately removing these addresses from your list to prevent further damage to your sender reputation.

August 2023 - SparkPost
Technical article

Documentation from RFC Editor explains that standardized bounce messages (Delivery Status Notifications) provide machine-readable information about delivery failures, enabling automated processing of bounces and identification of the failure reason.

September 2021 - RFC Editor
Technical article

Documentation from Microsoft explains that "mailbox unavailable" indicates the recipient's address doesn't exist. They advise verifying the address and removing it if the issue persists.

May 2021 - Microsoft
Technical article

Documentation from AWS explains that bounce codes provide specific information about why an email was not delivered. Understanding these codes helps in diagnosing and addressing deliverability issues related to the specific domain.

January 2025 - AWS