Microsoft update misclassifying Fastmail emails to Outlook addresses

We’ve noticed that a small percentage of emails sent to Outlook-hosted addresses are being affected again. We’re in touch with Microsoft and working with them to resolve it.

A recent Microsoft update is sometimes incorrectly flagging some emails from several providers, including Fastmail. This is causing intermittent delivery issues for some email sent to addresses hosted on [outlook.com](http://outlook.com). We are seeing a small percentage of outgoing mail affected, with no obvious reason as to why. Our team is actively working with Microsoft's email team to get this resolved as soon as possible.

Microsoft has addressed this issue and we believe the is now resolved. We continue to monitor.