Hope someone can help. Just in the last two days I have had problems receiving email from two domains (that I know of). The sender is getting this message:

The server was not able to deliver your email message 

 Subject: This morning 
 Date: Wed, 29 Mar 2017 09:15:45 +0100 



to the following addresses: 

 < email@michelleboard.co.uk > (mx.zoho.com: 451 4.7.23 Sender's SPF Policy F ailure)

I have always been able to get email from this domain. I have added the domain to my whitelist, but this doesn't seem to have helped.

Many thanks,

Michelle