Zoho mail - unable to send email to a customer. can send to other customers

Zoho mail - unable to send email to a customer. can send to other customers

This is happening only for 1 of our customers when we send them emails

This message was created automatically by mail delivery software.
 A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error.

 ERROR CODE :550 - 
136.XXX.XXX.XX is not allowed to
send mail from olympiagloves.com. Please see the SPF record, with scope
mfrom, identity , and ip 136.XXX.XXX.XX