Zoho does not send invitation email if meeting is created in calendar

Problem: I create a meeting in calendar and add attendees. After "Save" button it asks me if I want to send email to all ettendees, I click Send.

But none emails are sent. I did try that over outlook (connected thru active sync) or in zoho web mail. Nothing works.

What I do wrong? I need to send invites to all attendees.

Thanks