Starting somewhere today, it seems that the name email.freshdesk.com has been dropped from DNS. Mails from freshdesk are sent from email.freshdesk.com. This causes smtp servers to block mails from freshdesk - essentially rendering all email from freshdesk to be undeliverable.
Two possible sollutions:
- Stop mailing out from this non existent domain
- Make a dns entry to make the domain existent again.