When an outgoing email cannot be delivered, reviewing the bounce type and the recipient mail server’s response helps identify whether the failure is temporary or requires manual correction.

In BoldDesk, email delivery failures are categorized into the following bounce types:

• Transient Bounce
• Permanent Bounce

This article explains the difference between these bounce types, their common causes, and how to review email delivery failures in BoldDesk.

Understand Transient Bounces

A Transient Bounce occurs when an email cannot be delivered because of a temporary issue with the recipient’s mailbox, mail server, network, or delivery policy.

Depending on the sending email service and the recipient server’s response, the email service may retry delivery automatically. If the issue continues and the delivery service stops retrying, the message may ultimately be treated as a permanent delivery failure.

:::info
The number of retries and the retry period depend on the email service used to send the message. A transient bounce does not guarantee that delivery will eventually succeed.
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Common Causes of Transient Bounces

Transient bounces can occur for the following reasons:

• The recipient’s mailbox is full.
• The recipient’s mail server is temporarily unavailable.
• A network timeout or temporary delivery delay occurred.
• The recipient server temporarily deferred the email through greylisting.
• The recipient domain experienced a temporary DNS resolution issue.
• The recipient server temporarily rate-limited incoming emails.
• A temporary SPF, DKIM, or DMARC validation issue occurred.
• The email exceeded the recipient server’s message-size limit.
• A spam filter temporarily rejected or deferred the email.

Check the Delivery Status of a Ticket Message

You can review the delivery status of a specific outgoing ticket message from the Ticket Details page.

1. Open the applicable ticket.

2. Locate the outgoing message.

3. Select More Actions for the message.

4. Select Email Delivery Status.

5. Review the available delivery and failure information.

   

Understand Permanent Bounces

A Permanent Bounce indicates a non-temporary delivery failure that normally requires manual correction before the email can be delivered.

For example, an email may permanently bounce when the recipient address does not exist, the recipient domain cannot receive email, or the recipient server has permanently rejected the sender.

Common Causes of Permanent Bounces

Permanent bounces can occur for the following reasons:

• The recipient email address is invalid or misspelled.
• The recipient domain does not exist.
• The recipient account was deleted or deactivated.
• The recipient server blocked the sending address, domain, or IP address.
• The recipient server applies a strict anti-spam or delivery policy.
• The sending domain or IP address is blocklisted.
• The recipient domain does not have valid MX records.
• A recipient-server policy prevents delivery.

Resolve a Permanent Bounce

The appropriate resolution depends on the detailed response returned by the recipient’s mail server.

Use the following guidance:

• Invalid or nonexistent recipient: Correct the recipient email address or replace it with a valid address.
• Deleted or deactivated mailbox: Contact the recipient through another channel and request a current email address.
• Domain or MX record problem: Ask the recipient’s email administrator to review the domain’s mail configuration.
• Sender blocked by the recipient: Ask the recipient or email administrator to allow the applicable sender address or domain.
• Spam or policy rejection: Review email authentication, sender reputation, message content, and the recipient server’s delivery policies.
• Message rejected because of size: Reduce the message size or attachments before sending it again.

Do not continue resending an email to an invalid address without correcting the underlying issue.

Review Bounced Emails in Email Failure Logs

You can review transient and permanent bounce records from Email Failure Logs.

1. Go to the Admin Center.
2. Under General, expand Audit Logs.
3. Select Email Failure Logs.
4. Locate the failed email using the available filters, such as:
   • Ticket ID
   • Date range
   • Event Type
   • Bounce Type
   • Recipient
5. Review the Bounce Type and the detailed response returned by the recipient’s mail server.

Transient Bounce

Permanent Bounce

Understand the “Custom Bounce Code for Permanent Bounce Type” Message

The Custom bounce code for Permanent bounce type message indicates that the email provider returned a provider-specific response that BoldDesk classified as a permanent delivery failure.

This label does not identify one specific problem. The underlying failure may be an invalid recipient, recipient-server restriction, domain configuration problem, or another non-temporary delivery issue.

To determine the exact cause:

1. Go to Admin → Audit Logs → Email Failure Logs.
2. Locate the affected recipient.
3. Confirm that the Event Type is Bounce.
4. Confirm that the Bounce Type is Permanent.
5. Review the detailed SMTP response returned by the recipient’s mail server.
6. Correct the reported issue before sending another email.

For example, the following response indicates that the recipient mailbox does not exist:

550 5.1.1 The email account that you tried to reach does not exist.

For this response, verify the recipient email address for:

• Spelling errors
• Unnecessary spaces
• An incorrect domain
• An outdated or deleted mailbox

Update the recipient’s contact information with a valid email address before sending another message.

Review a Blocked Recipient Email Address

After repeated permanent delivery failures, an email address may be restricted from receiving additional outgoing emails.

If a valid recipient email address appears under Admin → Audit Logs → Blocked Email Recipients, first resolve the issue that caused the permanent bounce.

After resolving the cause:

1. Go to Admin → Audit Logs → Blocked Email Recipients.
2. Locate the recipient email address.
3. Review the reason for the restriction.
4. Remove the restriction if the unblock option is available and you have the required permissions.
5. If the unblock option is unavailable, contact BoldDesk Support and provide the affected recipient email address for review.

Understand Custom SMTP Delivery Status

When outgoing ticket emails are sent through a custom SMTP server, BoldDesk hands the message to the configured SMTP provider for delivery.

After that handoff:

• The custom SMTP provider handles delivery.
• The provider generates any bounce or non-delivery response.
• The final delivery or failure status may not be available in BoldDesk.
• The failure may not appear in BoldDesk’s Email Delivery Status or Email Failure Logs.

Review the following sources instead:

• The mailbox’s Sent Items or Outbox
• The custom SMTP server logs
• The email provider’s administrative portal
• Bounce messages or non-delivery reports

For more information, refer to Why Email Delivery Status Is Not Available for Custom SMTP Emails.

Frequently Asked Questions

1. What is the difference between a transient bounce and a permanent bounce?
   A transient bounce is caused by a temporary delivery problem, such as a full mailbox, temporary server outage, or rate limiting. A permanent bounce is caused by a non-temporary problem, such as an invalid recipient address, nonexistent domain, or permanent recipient-server rejection.

2. Will BoldDesk automatically retry a transiently bounced email?
   Retry behavior depends on the email service used to send the message and the response returned by the recipient server. Review the delivery status and failure details to determine the current outcome.

3. Does a permanent bounce always mean the recipient address is invalid?
   No. A permanent bounce can also result from recipient-server blocking, domain configuration problems, strict delivery policies, sender blocklisting, or other non-temporary rejections.

4. What does “Custom bounce code for Permanent bounce type” mean?
   The email provider returned a provider-specific response that BoldDesk classified as permanent. Review the detailed SMTP response in Admin → Audit Logs → Email Failure Logs to identify the exact reason.

5. What does SMTP error 550 5.1.1 mean?
   This response commonly means that the recipient mailbox does not exist or cannot be found. Verify the complete recipient address and update it before sending another email.

6. Where can I check the delivery status of one ticket message?
   Open the ticket, locate the outgoing message, select More Actions, and then select Email Delivery Status.

7. Where can I review bounced emails across the BoldDesk portal?
   Go to Admin → Audit Logs → Email Failure Logs.

8. Why is the final delivery status unavailable for an email sent through custom SMTP?
   BoldDesk can confirm only that the message was handed over to the configured custom SMTP server. The SMTP provider handles final delivery and bounce processing outside BoldDesk.

9. Can I unblock a recipient email address from BoldDesk?
   If the address appears under Admin → Audit Logs → Blocked Email Recipients, remove the restriction when the unblock option is available and you have the required permissions. Otherwise, contact BoldDesk Support.

10. Should I unblock an address before correcting the permanent bounce?
    No. Correct the underlying delivery issue first. Do not unblock an address that is invalid, nonexistent, or still rejected by the recipient server.

Related Articles

1. Why Email Delivery Status Is Not Available for Custom SMTP Emails
2. How to Troubleshoot Email Notification Delivery in BoldDesk