Greylisted, try again after some time

Greylisted, try again after some time

I am experiencing the same issue.
Mails sent from our server to Zoho is deferred.
These are simply emails sent when a user submits an enquiry form

B12DBC6B0C0: to=<********@japase.com>, relay=mx2.zohomail.com[204.141.32.121]:25, delay=4.3, delays=0.01/0.01/2.3/1.9, dsn=4.7.1, status=deferred (host mx2.zohomail.com[204.141.32.121] said: 451 4.7.1 Greylisted, try again after some time (in reply to RCPT TO command))