Email Authentication in ZohoCRM

You will now be able to authenticate your domains and subdomains. It will greatly reduce the chances of your email going to spam, and bring about better deliverability for your emails. To authenticate your emails sent from Zoho CRM, you need to validate the following authentication standards.

Domain Verification
DKIM (DomainKeys Identified Mail)
SPF (Sender Policy Framework)

You also have to follow these steps to authenticate email source

Adding company domain or subdomain
Verifying company domain details
Validating records
Visit the help document below for the details.

https://help.zoho.com/portal/en/kb/crm/connect-with-customers/email/articles/email-authentication

Zoho Email Config screen you'll see a link to validate your settings and here's a 3rd party site to check your settings: https://www.mail-tester.com/spf-dkim-check