Mail not delivered

Hi we are running a mailserver on  149.210.163.35. Message we are receiving from mailservers which are using messagelabs is: Cannot delivered, host not available. When using an other ip, it works. So we expect that our IP is on a blacklist. However that is not the case, please help to support us.

We checked our IP: The IP address you submitted, 149.210.163.35, does not have a negative reputation and therefore cannot be submitted for investigation.

kind regards,

Bas