Did you know that it does not take many complaints to cause deliverabiiity issues?
Our data suggests that a complaint rate of more than even 1 in 1000 can cause problems. This may happen as a consequence of direct actions by the ISP or as a reflection of something else. You may see issues mainly because you will be reported by recipients in a sustained trend. That is why it is extremely important to take action as soon as you start seeing several complaints come in because, as few as there are, it could spell trouble ahead and where there is smoke, there is fire.