Mails sent from Outlook - Zoho Mail Account are returning as undelivered

Mails sent from Outlook - Zoho Mail Account are returning as undelivered

Hi,

Getting this error on sending a mail to external mail IDs from Outlook for Mac.

ERROR_CODE :550, ERROR_CODE :5.7.1 This message does not have authentication information or fails to pass
5.7.1 authentication checks. To best protect our users from spam, the
5.7.1 message has been blocked. Please visit
5.7.1 information. q88si5315853pfa.222 - gsmtp