Since 22 December we have not been able to send email to Office365 email addresses - we get a message that our server is banned:
<firstname.lastname@example.org>: host sample.mail.protection.outlook.com[22.214.171.124] said: 550 5.7.511 Access denied, banned sender[xxx.xxx.xxx.xxx]. To request removal from this list please forward this message to email@example.com. For more information please go to http://go.microsoft.com/fwlink/?LinkId=526653. AS(1410) [SY4AUS01FT011.eop-AUS01.prod.protection.outlook.com] (in reply to RCPT TO command)
email address and our server ip removed for privacy
I have emailed firstname.lastname@example.org and followed all the steps, but the problem remains.
It seems others have had the same problem since 22 December: https://techcommunity.microsoft.com/t5/office-365/trying-to-find-help-for-550-5-7-511-access-denied-banned-sender/m-p/3046157#M37128
Can anyone shed any light on this, and how to get it resolved?