I have setup a dmarc record in DNS as follows:

Host - _dmarc.mydomainname

(I also tried - zoho._dmarc.mydomainname)

Value - v=DMARC1; p=none; sp=none; rua=mailto:my@emailaddress.com; rf=afrf; pct=100; ri=86400

However, I still receive a failure when I check my domain with mxtoolbox.

Please advise.

Thanks,

Chris