Until 2 December by home security camera sent email alerts to my iCloud mail accounts from another home email account which I also use on my Mac. Since then emails have been returned undelivered, apparently blocked by Apple. Test messages from my Mac to my iCloud account are similarly returned, though traffic is still being received in the iCloud account from other sources. The CCTV alerts are not being sent to the junk folder. How can I find out what is going on?
Below is the returned mail message I typically receive, Proofpoint tells me that the sovision SMTP mail server address, 18.104.22.168, is not blacklisted.
********* This is the Postfix program at host sv0.sovision.net. I'm sorry to have to inform you that your message could not be be delivered to one or more recipients. It's attached below. For further assistance, please send mail to <postmaster> If you do so, please include this problem report. You can delete your own text from the attached returned message. The Postfix program <email@example.com>: host mx5.mail.icloud.com[22.214.171.124] said: 550 5.7.0 Blocked - see https://support.proofpoint.com/dnsbl-lookup.cgi?ip=126.96.36.199: firstname.lastname@example.org (in reply to RCPT TO command) Reporting-MTA: dns; sv0.sovision.net X-Postfix-Queue-ID: B95E877C147 X-Postfix-Sender: rfc822; email@example.com Arrival-Date: Thu, 3 Dec 2015 11:10:00 +0000 (GMT) Final-Recipient: rfc822; firstname.lastname@example.org Action: failed Status: 5.0.0 Diagnostic-Code: X-Postfix; host mx5.mail.icloud.com[188.8.131.52] said: 550 5.7.0 Blocked - see https://support.proofpoint.com/dnsbl-lookup.cgi?ip=184.108.40.206: email@example.com (in reply to RCPT TO command) From: <firstname.lastname@example.org> Date: 3 December 2015 at 11:11:51 GMT To: <email@example.com> Subject: 00626E4841B8(Front) motion alarm at 20151203121146 ************