In the control panel in Troubleshooting -> Blocked accounts ( https://mailadmin.zoho.com/cpanel/index.do#troubleshoot/blockedaccounts) I attempted to use the Unblock function. However it resulted in an error saying it's a feature for a paid plan only.

So I purchased a paid plan and attempted to Unblock again, but this time the error showed "Sorry , we are unable to process your request, please contact support@zohomail.com"... Very dishonest way of promising a paid feature, then not delivering it.

I see that there are some replies here on the forums, so I'm trying my luck here. My e-mails to  support@zohomail.com and tickets using the support portal are still unanswered, after 3 days now.