Out of Office emails to GMAIL not working

When out of office is enabled. The users from gmail doesn't receive the out of office notification.

In message trace we get this Fail error:

Reason: [{LED=550-5.7.26 Unauthenticated email from <MY DOMAIN> is not accepted due 550-5.7.26 to domain's DMARC policy.
Please contact the administrator of 550-5.7.26 <MY DOMAIN> domain if this was a legitimate mail.
Please 550-5.7.26 visit 550-5.7.26 https://support.google.com/mail/answer/2451690 to le. OutboundProxyTargetIP: XXX.XXX.XXX.XXX.
OutboundProxyTargetHostName: gmail-smtp-in.l.google.com