Emails sent from a Plesk server to @hotmail.com or @outlook.com are delivered to the Spam folder or are not delivered with the following error message:
PLESK_INFO: Message could not be delivered to some recipients.
The following recipient(s) could not be reached:
Reason: 550 SC-001 (BAY004-MC1F30) Unfortunately, messages from
203.0.113.2 weren't sent. Please contact your Internet service provider
since part of their network is on our block list. You can also refer your
provider to http://mail.live.com/mail/troubleshooting.aspx#errors.
The same error message can be found in /var/log/maillog:
CONFIG_TEXT: Jan 1 00:28:34 jdoe postfix/qmgr: F2A22EA0FF8: email@example.com, size=616, nrcpt=1 (queue active)
Jan 1 00:28:34 jdoe postfix/smtp: F2A22EA0FF8: firstname.lastname@example.org, relay=hotmail-com.olc.protection.outlook.com[18.104.22.168]:25, delay=0.73, delays=0.57/0.01/0.11/0.04, dsn=5.7.1, status=bounced (host hotmail-com.olc.protection.outlook.com[22.214.171.124] said: 550 5.7.1 Unfortunately, messages from [203.0.113.2] weren't sent. Please contact your Internet service provider since part of their network is on our block list (AS3140). You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. [DB5EUR01FT015.eop-EUR01.prod.protection.outlook.com] (in reply to MAIL FROM command))
Emails sent to other mail services are delivered to Inbox folder without any issues.
@hotmail.com and @outlook.com are powered by Outlook.com. Outlook.com might block or treat emails from a server IP as spam according to their spam policy.
To get more information about the error, visit the Live Mail Troubleshooting page.
To resolve the issue contact Outlook.com support.