How to get your mails delivered to Microsoft’s SMTP servers
When setting up a new SMTP server (i needed one for my GitLab instance), sometimes it happens that you get a new IP address which was used before for sending spam mails – or other mysterious things which might end up at the blacklist of (major) email providers – like Microsoft. So i just found this:
<firstname.lastname@example.org>: host outlook-com.olc.protection.outlook.com[18.104.22.168] said: 550 SC-001 (COL004-MC6F4) Unfortunately, messages from aa.bb.cc.dd 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. (in reply to MAIL FROM command)
So… i am my own internet provider, what now?
After some time of searching, i found a list of multiple links to the Mircosoft Delisting Service – and none of them is working, except only one. If you want to save your time when having the same problem – here it is:
After using the form, it may take some time until the request is processed. After processing you will receive a mail from Microsoft with the confirmation or rejection. If successful, it would take up to 24-48 hours to be unblocked from all relevant mail servers.
As far as i know, this applies for outlook.com, live.com and hotmail.com email addresses.
Monitor your IP’s status
Microsoft offers mail server administrators the Smart Network Data Service platform (https://postmaster.live.com/snds/), on which they can register their IP addresses and view the corresponding status, e. g. whether the IP is blocked or not. It is also worth taking a look at the Junk Mail Reporting Program to find out which mails classify users of Microsoft mail services as spam.