Prevent email bounce

What is a bounce?

A bounce message, also called a Non-Delivery Report/Receipt (NDR), is an automated message from the recipient's email server with details about the specific problem regarding email delivery.

Emails can bounce if an email address does not exist or if there are technical problems with the delivery. This can have different causes, each of which may require different courses of action.

Whitelist for trouble-free email delivery

To be able to communicate with us smoothly, we recommend the following actions.

Please set the domains
maxcluster.de, hubspot.com, hubspotemail.net and sidekickopen.com
to the positive list of the e-mail server so that the e-mails are not blocked by the spam filter. We also ask you to classify the sender "maxcluster" as trustworthy.

Furthermore, we recommend whitelisting the following shipping IP addresses from HubSpot:

• 54.174.60.0/23
• 143.244.80.0/20
• 18.208.124.128/25
• 54.174.53.128/30
• 158.247.16.0/20
• 54.174.59.0/24
• 54.174.63.0/24
• 3.93.157.0/24
• 54.174.52.0/24
• 139.180.17.0/24
• 54.174.57.0/24
• 143.244.86.166

Measures for Microsoft 365

One way to prevent a bounce is to add maxcluster as a sender to your central or personal contact book. This will increase the trustworthiness.

Also, they can whitelist the above domains and IP addresses as follows:

• Log in to the management portal on your Office 365 mail server.
• Navigate to Management Centers > Exchange in the left menu.
• The Add Allowed IP Address window will now open. Add the IP addresses listed above.

If you have any further questions, please contact our support team at +49 5251 414130 or by email at support@maxcluster.de.