trouble with remove domain from zoho

trouble with remove domain from zoho

we used zoho to custom email with our domain. but now we moved to using our private mail server.
But some email can't send email to our mail server, some other can send.

We already deleted our account in zoho, and removed all zoho information in our domain setting.

our domain is watermelon.vn

Could any body help us? 

: Recipient address rejected: Greylisting in
effect, please come back later <<< 554 5.5.1 Error: no valid recipients ...
while talking to  mx2.zoho.com .:

>>> DATA
<<< 503 No recipients specified
451 4.4.1 reply: read error from  mx2.zoho.com .

Action: failed
Status: 5.1.3
Remote-MTA: DNS;  mx2.zoho.com
Diagnostic-Code: SMTP; 553 Relaying disallowed
Last-Attempt-Date: Sat, 7 Nov 2015 11:58:18 +0900