2017-07-27 21:16 UTC: Microsoft is currently blocking and/or throttling mail sent via our SMTP to hotmail.com, outlook.com, msn.com, and other email domains hosted by Microsoft. We’re working with Microsoft to resolve this issue and will update this post when more information is available.

2017-08-02 18:02 UTC: We’ve set up some downstream SMTP relays to help with delivery while we continue to work to get the main SMTP IP address unblocked.

2017-08-03 16:54 UTC:¬†Mail sent via our SMTP to hotmail.com, outlook.com, msn.com, and other email domains hosted by Microsoft is no longer being blocked or throttled. We’ll continue to monitor.