tucowsdomains.com

In April, some customers may have experienced intermittent DMARC failures on messages to Microsoft-hosted inboxes. Impact was most visible for senders with a DMARC policy of p=reject or p=quarantine. The root cause was related to how certain email headers were being handled. We have implemented a fix and will continue to monitor closely. While there may still be some residual impact to messages with elongated headers and as outstanding retries and queue delays clear over the next ~72 hours, we expect impact to remain limited.