Custom domain email

I cannot receive email from zoho mail..

Information

Domain
1. www.tdalert.uk

Have Try :
1. Test from mxtoolbox.com
Result
Both 10 /20 mx have point to the zoho mx.

Question
1. I try to send wrong email and the zoho mail have return message from mx.zoho.com
Seem it's work
2. But when i try email from zoho mail to my gmail and to reply back to zoho mail not work?
3.If the propagate issue involve, how long it's take.

Note
1. I follow this tutorial
https://www.digitalocean.com/community/tutorials/how-to-set-up-zoho-mail-with-a-custom-domain-managed-by-digitalocean-dns

Have solve it..

The information provide quite difficult to understand.

First
1. If you register with xxx@gmail.com.
2. Don't sent to xxx@gmail.com. It will said some weird thing..

Email Sending
1. Seem quite slow around 10 to 20 second.. In my back end , i will try to create a queue cron tab to schedule each 10 minute if got checking new email and send via zoho smtp. Seem much difficult but just preventative if failure.