Getting 550 5.7.1 Access Denied error when sending to @ucdavis.edu

Getting 550 5.7.1 Access Denied error when sending to @ucdavis.edu

Whenever I send emails from my Zoho email I get an undeliverable email back with the error code 550 5.7.1 Access Denied. What am I doing wrong it works everywhere else. I set up a domain key and SPF record.