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.
If any recipient is marked as blacklisted (for example, due to a BOUNCE or a COMPLAINT where the recipient flagged a previous email as spam), the email will not be sent.
Why does this happen?
Blacklisted recipients cannot receive emails from Kolleno.
To protect your domain reputation and ensure deliverability, Kolleno blocks the email until the blacklist issue is resolved.
How to resolve
Review the list of recipients.
Identify the one(s) flagged as blacklisted.
Remove or update the blacklisted recipients.
Re-send the email once all recipients are valid.
⚠️ Important: Kolleno will only send the email if every recipient is cleared from the blacklist.