I get this error sending emails to Hotmail addresses.
550: 5.7.1 Unfortunately, messages from [34.2.94.17] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3150). You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. [Name=Protocol Filter Agent][AGT=PFA][MxId=11BD4E6CEEB38F5C] [DS3PEPF0000C37D.namprd04.prod.outlook.com 2026-05-08T09:35:13.952Z 08DEA7367DF30CA6]

Can Yahoo please fix.