I can not send email from zoho, but I can receive !

I can not send email from zoho, but I can receive !

Hi, I want to use ZohoMail for my domain, I bought domain from namesilo.com and i have added your MX records on Friday, so as I know it would take some time to take effects since DNS Updates it can take up to 48 hours, so it's been more than 48 hours and the problem it is that, I can send emails for example mike@mydomain.com to mike@gmail.com, but I can not receive emails to mike@mydomain.com !?
Help me out to fix this problem !