10/5/2023: As of 9:15 PM EDT all suppressions related to this error have been removed. Thank you for your patience and we apologize for any frustration caused. If you continue to see any errors similar to the error below, please contact Support.
10/5/2023: Our team is aware of an issue where recent sends to Microsoft's webmail domains (i.e. @hotmail.com, @outlook.com, @msn.com) have landed in suppressions tied to an IP error.
We are actively collaborating with our sending provider and Microsoft to rectify this situation swiftly, with our primary goal ensuring that any flags on affected IPs are promptly removed.
Once we've received that confirmation, we will bulk remove suppressions for any users affected by this issue. If you have any follow-up questions, please do not hesitate to contact Support. We will update this Known Issue once we've bulk removed suppressions across all affected sites.
5.7.1 Unfortunately, messages from [###.###.##.##] 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.