Can't send emails through Office 365 SMTP - Client host blocked using Spamhaus
Windows server and Kyocera photocopier can no longer send emails through Office 365 SMTP server (domain.mail.protection.outlook.com). The issue started happening after ISP change (new ISP was UK's PlusNet). After checking PowerShell mail send script output I found following error:
Exception calling "Send" with "1" argument(s): "Mailbox unavailable. The server response was: 5.7.1 Service unavailable, Client host [80.229.xxx.xxx] blocked using Spamhaus.