Ariel Costas

Outlook blocked my IP address once again

By Ariel Costas - September 24, 2021

As you’ve read on the title, my VPS’s (where this website is hosted) IP address has been blocked once again by Microsoft Outlook without notice. I’ve detected this issue tonight while trying to send an email to an account hosted on, but this also happens for any domain hosted under MicroShit’s servers. The following message was returned to my MTA (Postfix) when sending the email:

: host[] said: 550 5.7.1 Unfortunately, messages from [ThisServersIP] weren’t sent. Please contact your Internet service provider since part of their network is on our block list (S3150). You can also refer your provider to [] (in reply to MAIL FROM command)

I’ve already contacted my provider to see if this can get unlocked. But in either case, people should be concerned about this: a company decides to block incoming email to all their servers (and thus for their users/clients), cutting communication because they “consider it spam” (as if there weren’t things that can be done against that).

Some people have told me to stop self-hosting my email because I’ll stop having these kind of problems. That would be nothing but a lose for myself and for digital freedom and independence: accepting that some corporations have the power to block you if they want, and you just accept it.