If you use custom DNS for sending emails, when you send an email in Kolleno to multiple recipients, the system checks each recipient against blacklist records.
Emails may fail to send because one or more recipients are marked with status BOUNCE or COMPLAINT.
It’s important to understand how Manual and Workflow emails handle these contacts differently so that you can resolve blocked communications.
Manual Email Sending
When sending manually, the system will:
Send the email to all valid recipients.
Exclude recipients with BOUNCE or COMPLAINT status.
Generate an inbound delivery failure notification for the blocked contact.
Mark the outbound email with the status BOUNCE/COMPLAINT for visibility.
Result: Other contacts still receive the email.
Workflow Email Sending (Custom DNS Only)
When using custom DNS email addresses, workflows behave as follows:
If any contact in the Configuration → Customer Contacts list has BOUNCE or COMPLAINT status, the entire workflow email is blocked.
No recipients receive the email.
A workflow note is created showing the error:
EMAIL in the workflow 'Workflow_Name' could not be sent.
Email address 'Target_Email_Address' is blocked due to status: 'BOUNCE' or 'COMPLAINT'.
Result: Workflow emails fail completely until the invalid contact is removed.
How to Fix a Blocked Workflow
You can find more detailed guidance in the following Help Centre article:
“Email Sending Blocked Due to Blacklisted Recipients”