Overview
SPF Records configure which servers are allowed to send email on behalf of a domain.
Complete SPF
This will catch all zoho applications
v=spf1 include:one.zoho.com ~all
ZOHO Applications
ZOHO One
include:one.zoho.com
ZOHO Mail
include:zoho.com
ZOHO CRM
include:transmail.net
ZOHO Desk
include:spf.zoho.com include:transmail.net
ZOHO Subscriptions
include:zoho.com
ZOHO Books
include:sender.zohobooks.com
ZOHO Campaigns & Marketing Hub
include:zcsend.net