A serious question about Zoho

A serious question about Zoho

I have used your service for a long time and I am just noticing that recently a lot of sites are banning your domain and classifying it as an illegal domain.  I find this very troubling to say the least.  The latest one to do that is Swagbucks.com and I was told they no longer allow people with your email service on their service EVEN THOUGH I have used your email with them for about 4 years (from day one with them).

Does anyone have an idea what is going on and why this is suddenly happening?