S.O.S: Can Receive Emails but not Send (No Error Shown)

S.O.S: Can Receive Emails but not Send (No Error Shown)

Team;

We have our email server for acodeidea.com on zoho.

I can receive emails but not send them.

However there is no error when sending emails and the mails are in the sent box.

Also, we are able to send and receive email within our organization. 

But NOT to gmail or email hosted on google servers.

Can someone please help...???

Note: Checked the MX records and they are fine. The problem persists for over 24 hours now. 

Best regards,
Naveen