Zoho Mail Slow Working Problem

Zoho Mail Slow Working Problem

Hello,

I have moved mail server of my company into Zoho Mail completely today, i noticed something; when i got lead, mail notification was coming quickly in same minute before on yandex server but after this changing maybe it comes after 20-30 min. later. I don't know it's about zoho mail server but even thogh i tried a few times, i got same results. 
I have added an example, created time is 00:13, mail notification time is 00:30 so 17 min. later. I think it's quite late for response to client. Because we are working 7/24

Have you any idea or same problem about this?