Emails rejected by Yahoo now

Emails rejected by Yahoo now

Emails we've sent to Yahoo users through sender1.zohomail.com are being rejected by Yahoo.  I am assuming this is due to the multiple DNSBLs Zoho is apparently on all of a sudden.  What is being done to work this issue with priority?

Here is what we're getting back from the mailer-daemon,

    ----- The following addresses had fatal errors -----    
   [Status: Error, Address: <userxxxx@yahoo.com>, ResponseCode 421, 4.7.0 [TS01] Messages from 74.201.84.158 temporarily deferred due to user complaints - 4.16.55.1; see http://postmaster.yahoo.com/421-ts01.html]

Message will be retried for 4 more day(s)