Problems with Zoho mail

I have a blog with wordpress.com and I purchased a domain with netregistry.com.au. I recently mapped the domain. I successfully registered with Zoho email to get my custom domain email address. When signed into wordpress, I visited store>mydomains>edit domain>edit DNS. As per Zoho email setup advice, I added 2 MX records: 1. mx.zohomail.com at priority 10 & 2. mx2.zohomail.com at priority 20. I seem to be able to receive emails but unable to send them. I don't get any email errors or bounce back errors. However, nothing seems to happen once I send an email from Zoho. Please help.. how do I send emails from my custom email address with Zoho