Configuring Dual Delivery in Google Apps / Issues to send to same domain addresses / receive works perfectly

Configuring Dual Delivery in Google Apps / Issues to send to same domain addresses / receive works perfectly

I followed this zoho  guide to configure dual delivery at Google Apps it seems to work perfectly to send and receive emails to all external domains from the zoho account, the only problem is when sending an email from a zoho account with our domain example.com to an address with the same domain but hosted at Google Apps it returns a " Undelivered Mail Returned to Sender" error. For any other domains it works perfectly.