Wow! This is not good at all. I had originally notified you over a year ago that this was coming, and was assured it would be handled. I renewed enterprise licensing based upon that promise. I referred you to Truckhunters.com so they could integrate ZOHO with their newsletter mailing. This is a feature that I already bought when I bought into ACY Mail, and now you will not maintain it without me paying extra as if it a new feature request.
Since you explain you can do it for extra money, it is clear this is not really a time budgeting issue. It's just not worth it to you to keep the product up-to-date and functional for what has already been bought?
This is very poor business practice. Please revisit this.