From today, any emails we send to our TeamInbox addresses fail to be delivered.

Our TeamInbox is connected via IMAP to 2 x Zoho Mail accounts. If I log in to those accounts directly via Zoho Mail, I can see all the emails landing in the inbox.

The emails are never delivered to TeamInbox. I checked IMAP settings and everything looks good. This has broken overnight with no settings being changed from our end.