What are Bounce errors?

If you've encountered one of the following errors when using Closum - DNSProblem, ConnectionProblem, BlackListed, AccountProblem or ConnectionTerminated - this article will explain what each one means and how to solve the problem.

DNS Problem

This error indicates that there has been a failure in DNS (Domain Name System) resolution. This means that the domain or subdomain configured may be incorrect, not propagated correctly or not exist.

Possible causes:

• The domain is not configured correctly.
• The DNS server is temporarily unavailable
• Connectivity problems with the DNS provider

Solution:

• Check that the domain or subdomain is correct
• Use a DNS verification service to check for propagation failures.

Connection Problem

This error occurs when the system is unable to establish a connection with the server.

Possible causes:

• Problems with your internet connection
• Firewall or antivirus blocking the connection

Solution:

• Check that your internet connection is active
• Try accessing Closum from another browser or device
• Temporarily disable the firewall or antivirus to test whether they are interfering

Black Listed

This error indicates that your IP or domain has been blocked because it is on a security or spam blacklist.

Possible causes:

• Your IP has been flagged as suspicious for unusual activity
• Your domain has been blacklisted by an email server
• Excessive Email sending may have triggered automatic blocks.

Solution:

• Check if your IP is on a blacklist using services such as MXToolbox
• If you are sending Emails, reduce your sending rate to avoid blocks
• Contact Closum support to request that the block be removed

Account Problem

This error indicates a specific problem with your Closum account.

Possible causes:

• Your account may be suspended for non-payment
• Unauthorised access or security lock
• Login authentication error

Solution:

• Check your account for financial issues
• Try resetting your password and logging in again
• Contact Closum support for more details about the problem

Connection Terminated

This error occurs when a connection that had already been established is abruptly terminated.

Possible causes:

• The server closed the connection due to inactivity
• The connection was interrupted due to internet instability
• The system detected a suspicious access attempt and blocked the connection.

Solution:

• Try reloading the page and redoing the action
• Make sure your connection is stable

Deletion

The Email address has a blocked status in your account, the Email was cancelled or we were unable to deliver it within 48 hours.

Possible causes:

• The recipient has blocked the sender's emails.
• The Email was cancelled manually.
• The server was unable to deliver the Email within the time limit.

Solution:

• Check that the recipient's Email address is correct.
• Ask the recipient to check their spam folder and remove any blocks.

No mailbox

The Email address doesn't seem to exist. It may be misconfigured or have been removed from the server. Receiving this error will permanently set the status of this contact to invalid.

Possible causes:

• The Email address has been entered incorrectly.
• The Email account has been deactivated.

Solution:

• Check with the recipient that the e-mail address is correct.
• Remove invalid contacts from your list to avoid future problems.

Account problem

There is a problem with the recipient's mailbox, e.g. the mailbox is full and cannot receive any more Emails. In most cases, this means that the Email account is no longer in use. Closum may try to resend the Email automatically, depending on the server's response.

Possible causes:

• The recipient's inbox is full.
• The Email account is no longer in use.

Solution:

• Wait a while and try to resend the Email.
• Contact the recipient to check that the Email is still valid.

Spam

The Email was rejected because it corresponds to a profile that the Internet community has classified as spam.

Possible causes:

• The content of the Email contains suspicious words or links.
• The sender has been marked as spam before.

Solution:

• Review the content of the Email to avoid terms that trigger spam filters.
• Ask recipients to add your Email to their list of trusted senders.

Code Error

The Email was not delivered due to a technical problem in the sending system.

Possible causes:

• An internal error in the sending system.

Solution:

• Contact the Closum support team for analysis.

SPF problem

The Email was not delivered because there was a problem validating the SPF record of the domain of this Email.

Possible causes:

• The sender's domain does not have a valid SPF.

Solution:

• Configure your domain's SPF record correctly.

If you're still experiencing difficulties with any of these errors, our support team is on hand to help! Get in touch via our Support Centre for personalised assistance.

Updated on: 08/07/2025