Im having the mentioned issue for couple of weeks now, 

Error, ERROR_CODE :554, ERROR_CODE :5.7.1 Message refused by DNSBL check. dnsbl-1.uceprotect.net / 74.201.84.162 This email has been rejected. The email message was detected as spam. 

74.201.84.162 has been blacklisted by   SPAMCANNIBAL , and   UCEPROTECT for a few weeks now. Important emails are getting bounced back.

I have so far sent 3 emails to zoho though various support/help portals and have had no reply so far.

Can you guys please look in to this and resolve this ASAP ?