Hello there Our modoboa mail server in digital ocean recently got a security certificate error, so we had to shut it down. We set up a zimbra mail server in the new droplet we opened in digital ocean. Although two months have passed, we still cannot send mail to ms mail distributions such as outlook and hotmail. We are getting the following error. I tried every way from my DNS records. Outlook has confirmed that such a problem is unlikely, there is no blockage in digital ocean but I still get the following error. outlook-com.olc.protection.outlook.com[188.8.131.52] said: 550 5.7.1 Unfortunately, messages from [-ip-] weren’t sent. Please contact your Internet service provider since part of their network is on our block list (S3140). You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. [SN1NAM02FT0047.eop-nam02.prod.protection.outlook.com] (in reply to MAIL FROM command)
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