I just helped a local business set up a paid Mail subscription. They were previously using email included with their web hosting package and those IPs recently got blacklisted due to spammers using the same shared server. We moved them to Zoho to avoid their email getting bounced.

As soon as it was all setup I did a deliverability test via MXToolBox and found that one of Zohos IPS is blacklisted at SORBS. I emailed Zoho support about it few days ago since they have to submit a request to have the IP delisted. So far no response at all. Thankfully it's just on one blacklist, which is far better than the previous hosting, but it's still an issue that needs resolved and Zoho doesn't seem to be responsive at all. Maybe there never got the email. It could have been bounced since the server is blacklisted.