Our domain was abruptly blocked by our registrar this morning. Our NOC team and myself tried to get in touch with them and they tell us "Contact our legal". Even I could not get in touch with anyone beyond their phone operator. The domain was restored, but as DNS takes time to restore, we are still facing issues. They later claimed there were abuse complaints about Zoho.com emails (which is our personal email service with millions of free and paid users). We received a total of 3 complaints from them and two of them have been acted upon and one is under investigation.
Once we dig our way out of this, we will find ways make sure no one takes down our domain again this way.
While the fight against it is rather dire and no end will ever be in sight, I'll nonetheless never stop (tool assisted) fighting.
Anyway, @zoho.com addresses used by spammers started to pop up circa a month ago and increased rapidly in occurrence. As we use stopforumspam to report and track spammer info (and surely are not the single forum seeing those @zoho.com domains) you may got a few flags raised somewhere.
Not sure what caused this sudden (from our POV) attraction of spammers using zoho, you may want to look into some defense against this. While a full solution may not be achievable it's often enough to be faster than other providers, aka the tiger defense ;-)
Thank you for your notification, will check on this and block those who spam using our system. However please put up an email to abuse at zoho.com so it would help us provide clue to our investigations. Reg Rajasekar Zoho Abuse Monitoring Desk.