Just received this from postmaster@outlook.com:
Delivery has failed to these recipients or groups:
report_spam@hotmail.com
Your message couldn't be delivered. Despite repeated attempts to deliver your message connection time outs with the recipient's email server prevented delivery.
Contact the recipient by some other means (by phone, for example) and ask them to tell their email admin that it appears that their email system is timing out when your email system is trying to connect to it. Give them the error details shown below. It's likely that the recipient's email admin is the only one who can fix this problem.
report_spam@hotmail.com
10/7/2021 8:17:21 AM - Server at MN2PR21MB1230.namprd21.prod.outlook.com returned '550 5.4.315 Message expired, connection timed out(Socket error code 10060)'
10/7/2021 8:07:21 AM - Server at xmr-internal.protection.outlook.com (10.233.166.17) returned '450 4.4.315 Connection timed out [Message=Socket error code 10060] [LastAttemptedServerName=xmr-internal.protection.outlook.com] [LastAttemptedIP=10.233.166.17:25] [CB1PEPF00003800.namprd00.prod.outlook.com](Socket error code 10060)'
Microsoft's CERT form (https://msrc.microsoft.com/report/abuse) was also down for a whole day because one of their JS resources failed to load.
What's going on with Microsoft?